Last time I checked, unlimited data was off the menu for non-mobile phone devices. Anyone know if this has changed recently or where might be a good place to find out what the cheapest data only deals are?

On moneysupermarket.com you can review mobile broadband plans, which are the dongles.

Ordered by price, you can get a Vodafone 18 month plan for £7.50 per month, which includes 2GB per month.

Alternatively, Three do a 10GB plan, 1 month rolling contract for £15 per month.

There are others, so pop onto their website and take a look.

Giffgaff... £5 for 500mb data, £7.50 for 1GB or £12.50 for 3GB.. Or T-Mobile do an iPhone MicroSIM where you topup £10 once and get 500mb a month for a whole year, yes you heard that right £10 a year for 500mb every month.. My mate uses it and it works great! see here: http://www.t-mobile.co.uk/shop/micro-sim/ - I usually wouldn't advise T-Mobile and this plan does have the 3.8mbps speed cap but for £10 a year i think u would be silly not to TRY it

Surely it'd be cheaper to add unlimited data to your current mobile phone plan and use your phone to tether. E.g One Plan/Full Monty.

Because no company other than three allow more than 5gb per month on a dongle . Here is a list of the best MBB deals.

Three offer 10GB for £15pm (1 Month)
Giff Gaff offer 3GB for £12.50pm (1 Month)
Orange offer 5GB for £30pm (1 Month)
O2 offer 1GB for £10 i think (1 month)
Voda offer 2GB for £15pm (1 month)

In the end it will all depend on the signal you get with each provider so make sure you know what type of signal you'll get.

IMO You can get the One Plan with Three (£25pm) or the full Monty with T-Mo (£26pm) data which include unl internet and tethering (or an Orange/o2 plan with 2GB). Just use the plan in your phone like you're supposed to and tether it as a mobile dongle when you need too. Two birds one stone

O2 and Orange offer plans with 2GB internet for phones with tethering as well.