You'll most likely get scrap rate for them, because they cannot easily be reused. Platinum is not an easy metal to just melt down and recast, it has to be re-refined before it can be reused.
It's around $1400ish right now per ounce, pure, and you won't get that per ounce (that's pure, unalloyed and not used). Your best bet is to take it to a few places that will buy metals and get a few quotes to see what they will offer, and take the best offer. I couldn't give you a guesstimate because I don't know what you have, I can't feel the items, and I don't know about what UK going rate would be.