I have a personal BB 8700g on T-Mobile in UK - I'm paying around £25 per month on a deal I started about 18 months ago. I chose T-Mob because they give an inclusive email allowance of a whopping 50MB per month which is higher than any of the other UK carriers who all offer in the region of 6MB.
With T-Mob if you want email only it's a fixed monthly cost of £17, otherwise if you want voice and text as well you choose a package and (they start at £20 per month) and then add £10 per month on for email/internet.
It's all on Mobile Phones - T-Mobile Internet and Email - T-Mobile
. I'm looking to upgrade to the new 8800 but only UK carrier to stock it currently is Vodafone which I don't think is as good a deal (for personal use) as T-Mob.
Hope this helps you.....