Erm I would think any router that will work with NTL BB will work as by the guides on the
PSP site there is an ethernet port on the PSP.
All you do is connect the PSP to a LAN connection on the router. If you want to keep cables to a minimum you could go wireless but that's more expensive. Do a search for Router in articles and the computer area of the fourm and you will find loads of threads about routers.
http://www.cableforum.co.uk/board/article.php?a=74