The key to cheap broadband is to snap up short-lived promo deals, and right now there are two corkers. As always they come with line rental, and as that's far cheaper than getting broadband alone, you could just not plug in the phone.

The possible savings are huge, as many don't realise how much they're shelling out already. So here are the typical prices of the big firms' standard contracts including line...

- BT: £41/mth (£492/yr) or £47.50/mth (£570/yr) on fibre broadband
- TalkTalk: £25.50/mth (£306/yr) or £32/mth (£384/yr) on fibre broadband
- Sky: £29/mth (£348/yr) or £39/mth (£468/yr) on fibre broadband
- Virgin: Up-to-100Mb fibre £40/mth (£480/yr)

Now compare those to the hot promo deals below...

1. New. Code for Sky newbies gets b'band & line for '£10.33/mth' (£124/yr). MSE Blagged. Grab a code via this Sky link* and apply by Fri 26 May for a 1yr deal offering up-to-17Mb speed broadband with unlimited downloads.

- It's only for those who've not had Sky in the last 12mths. If you fit the bill it's available to 90% of the UK - you're told if you can get it when applying. (Existing Sky customers see how to haggle below.)
- Half-price line rental. Usually £18.99/mth, here £9.50/mth fixed for the year. Call costs are a touch more than BT - see Sky call costs.
- 'Free' broadband for a year. After the contract it's £10/mth.
- You pay £9.95 router delivery and £5 (that's refunded) card verification.
- No line/switching from cable? There's a £20 new line fee.

Cost analysis: With the router cost it works out £10.33/mth before calls (and line fee if needed).

2. Ends Thu. BT fibre b'band & line pay £408/yr but get £200 back so equiv £17.32/mth. Fibre broadband is much faster and good for heavy downloading, streaming, gaming or multiple users. Apply before the end of Thu via this BT link* and you get up-to-52Mb fibre (3x normal speed) on a 1yr contract...

- It's for anyone not currently on BT broadband. So just a BT line for calls is fine. If you fit the bill, 83% of the UK can get it - you're told if you can when applying. (Existing BT broadband customers see how to haggle below.)
- Standard BT line rental, currently £18.99/mth. Weekend calls to UK landlines are included - for others, see BT call costs.
- Fibre broadband £10/mth for the year. After the contract ends you pay its standard rate, currently £28.50/mth.
- £59.99 set-up. Incl activation and 'free' router p&p.
- Get £200 on a prepaid Mastercard but you MUST claim it. This is what makes the deal hot, but as BT won't remind you, diarise to use this Mastercard claim link within 3 months of activation (the card takes up to 30 days after to arrive).
- What if BT hikes prices? Sadly they can, but you can leave penalty-free if that happens and keep the Mastercard.

Cost analysis: It's £407.87 over the year before calls. But claim & use the Mastercard (anywhere that takes Mastercard so it's almost as good as cash) & it's £207.87, equiv to £17.32/mth.

Halve broadband costs or treble the speed
Halve your broadband cost or treble the speed

3. 10 ways to haggle down broadband costs, but for you we'll do it in 9. Sticking is easier, especially if you're happy with service. Luckily big broadband firms have some of the easiest call centres to haggle with. In our last poll 87% of you said you'd had success haggling with Sky, 78% with BT.

Like Shelly, who wrote: "Thanks to your suggestions, we haggled a much better deal with Sky - replaced ordinary broadband with fibre and are now paying £15/mth less."

For full details see our How to haggle down your broadband guide, but here's a taster of 9 quick tips.

i) The best time to do it is when you're near the end of your contract.
ii) Check out competitors' prices first using our Cheap Broadband guide.
iii) Mention anything that's annoyed you such as price hikes or poor service.
iv) Use phrases that pay such as "It's out of my budget" or "I want to stick with you but my partner doesn't - can you help?" See full Phrases that pay.
v) Be firm and polite, not angry; you're trying to charm them into a discount.
vi) THE BIGGIE: Say if the deal isn't good enough you'll have to leave. That way you get put through to 'disconnections' - its real name is customer retentions, their job is to keep you. See Retention tricks.
vii) If at first you don't succeed, try another day - rumours are they work on quotas.
viii) Don't call in lunch hours: that's often when they're really busy.
ix) If the deal really isn't good enough, do consider actually leaving.

4. Check if your broadband speed is fast enough. Do a free 2-min speed test* to see how speedy your broadband actually is (try at different times of day for the best picture).

If you're signing up to a new provider, it's tricky to know what speed you'll actually get. There's a rule that only 10% of customers need to get advertised 'up to' speeds, though this is currently under review. Some providers give you a minimum speed at sign-up, and if you get speeds "significantly below" that, you may be able to leave penalty-free.

To find out your rights, see our Testing Your Broadband Speed guide.

5. 14 tricks to boost your broadband speed. Little things can make a big difference. Try moving your router or boosting your signal with a free widget. See Broadband Speed Boosting Tricks.

6. What does 'available to XX% of the UK' mean? Firms tend to be only able to give really cheap prices if they have their own kit in the exchange cabinets on the streets - called 'unbundled exchanges'. Otherwise the service isn't usually available, or it's at a much higher price - you're told during sign-up.

7. Is cashback possible? Members of top cashback sites may be able to get bigger cashback through them. It's worth checking, though do compare like-with-like, eg, check the prices and contract lengths are the same - you may find you get more cashback but are locked in for longer.

This article first appeared in the weekly email on 17 May 2017.