Sony Ericsson :: ELM Internet Access And PAYG

First off, a bit of background. I bought an ELM (unlocked) off of eBay. I was able to put an ASDA sim in and it is fine for calls etc. However, I'm very puzzled as to what is going on with the internet settings. I contacted ASDA and they sent the appropriate setting for my phone but whenever I try to use Opera Mini , Bolt, GPS or anything else Internet related the connection fails almost immediately. What doubly puzzles me is that if I press the O2 softkey a page comes up which says 'It looks like your using wifi (which I'm definitely NOT) but then that page allows me to browse to other pages (BBC etc). The phone has clearly originally been on O2 and it's almost like something in there has grabbed the internet and won't let go so it's the ONLY internet page I can access. I've tried hard resets as suggested by ASDA etc.