I can't be the only one who thinks some of this info is a bit iffy. Since my last post was ignored I'll start again and try to be more informative.
You could choose 3 of your choices from COWI and pick the other two as back ups. Personally I think you want a semi easy one to get into which isn't UCL, Bath or Bristol as you were talking about up there. They're all pretty difficult to get into even if their offers do tend to be 'easier' so hardly safe options. I'd advise having one option as a lower down uni like Nottingham, Manchester, York, Exeter, something like that. They're all relatively easy to get into but quite respected choices nonetheless. Which leaves your final choice; a uni which fits between COWI and your backup. This is where I'd actually use Bristol, Bath, UCL or maybe even Durham. Bristol would be my choice based on lack of STEP though.