Well I've found '55' and '12.8' on the bottom bracket however I read some Bottecchia's are stamped with the tubing (slx, tlx etc) used so I may investigate further.

I have found a 1988 Bottecchia on ebay that looks very much like the frame matches mine - I'm further persuaded by the fact mine used to be red and this one is also so I've emailed the seller asking for some large pictures. If I get any and it matches I'll put them up to show what the frame/bike used to look like.

Thanks for everyone's insights and opinions so far.

What's the opinion on Bottecchias?
How much is too much to have paid for this frame? - for reference I paid just under £20 so about $30.