I was hosting with one of the big boy hosting companies called UK2.net for my PHPBB link exchange forum but was having issues with speed and performance.
I decided to move my forum site to a reseller after reading another thread on this site. The provider i read some good reviews on was andthenhost.com. They also have a 1 click install option for PHPBB which would have made my life easier at the beginning instead of having to teach myself MySQL and PHPBB install lol
They offer a standard package for PHPBB forum beginners at 99p a month and when your site becomes bigger you can easily upgrade.
The link for 99p hosting is http://andthenhost.com/99phosting.html
I have also just done a deal to have there advert on my forum in exchange for unlimited bandwidth wah hay
If you do use these chaps make sure you select my website address "http://www.linkexchangeforum.co.uk" as a referral as I get my hosting for free after 5 referrals