Car appreciation... the aesthetics, the engineering, etc

I'm not an air con expert, but this sounds like you paid for a re-gas then the gas leaked (£60 is going rate).

If you don't use the air con for a while (e.g. between the end of summer and April) the seals can dry out and leak, but it could be a bigger problem.

When it stopped working last year you could hear it 'try' but air didnt get any colder, now when you hit the button absolutely nothing changes

This sounds like the compressor was running but now isn't. Depending on what car you've got you could google common problems and do some fault finding yourself.