The bubbles are from rust underneath the paint. It doesn't appear to be too deep though and I plant to do a little sanding in that area first to see how bad it is. Inside of the tubes look to be fine.

I've also sent a friendly e-mail to the shop I bought it from. If I'm lucky they might reply with some info.

Thought some of the knowledgeable folk on here might be able to id frame builder from the pics in the flickr link but realise as it's not high-end then this could be near impossible. I'll throw up some pics of the complete bike as well.