Looks like a fantastic space and am sure you will get a lot of enjoyment out of it.
One thing I would suggest, still in line with your bang for buck policy but on the higher end. Try and squeeze a 4k projector into the budget. I bought my 1080p Sony projector about 2 years ago and whilst its fantastic most peoples main reasons for not getting 4k (aside from price of course) is lack of content and unable to tell the difference on whatever screen size they choose. Content is now coming along since 4K Blu-Ray has been officially released and most of the big new released will be arriving in this format plus even going for the smaller end of a PJ screen say 90" you will definitely notice the difference.
Wouldn't necessarily suggest a Sony as they are still around £5k for their cheapest 4k but look around for cheaper alternatives as it will be one of the biggest things you can do as far as future proofing go.
Good luck with the setup and enjoy