Any recommended monthly only ones? Cheapest I found was £11 a month for 1GB.

I got a Three 12Gb valid for 12m, pay in advance, £70. That’s me sorted on the weekly london-bound train journey for a year.

I have had a Three mobile Wifi device for a year, fantastic. You have to pay for the unit (£75 when I got mine) and then it’s £15 month on a rolling monthly contract. It’s very flexible as you can connect multiple devices at once and Three is much faster than other 3G providers. Of course you have to check Three coverage in your area but I’ve found it very good in London (obvious), Kent, Surrey and Hampshire (except in real rural areas)

Giffgaff is a bit cheaper. http://giffgaff.com/goodybags

just about to pop out, but there’s a cheaper way to do it… I’ll post it when I get back

If you can use your phone contract and just tether then that’d be my preferred option (and is what I do). Doing it that way I can get unlimited data for £15 a month which is waaaay better than any dongle deal I’ve seen!

Sorry about that…. Popped out for longer than I anticipated, then forgot what I was doing…

Buy an unlocked dongle from amazon/ebay/similar, then you can use any old sim cards you like.
The cheapest way I have found to do it in this country is to by the 3Mobile sim cards preloaded with 3gb/3months of access. These just stop working when either you have used all the data or you reach three months. You can then just buy top up data/pay as you go or similar… Howevere, the cheapest thing to do is just to chuck it away and put a new one in with another 3gb/3 months worth of data preloaded. They currently cost £21 from 3 or £11-odd from Amazon. Buy them from amazon and it works out at £3-4 (per month/per Gb). I just buy 2-3 at a time, keep one in my iPad (which doesn’t need a dongle) and keep a spare tucked behind the cards in my wallet. If the one in my iPad runs out I just chuck it away and put the next one in.

Slightly more faff but much cheaper.