It looks like it should work. It'd be a cheap way to get discs on the puppy. And if for some reason it doesn't fit, sell the adaptor. You'd only lose a couple of £'s.
The frame angles shouldn't matter, as basically the adaptor takes the inside dropout face and the wheel spindle as its two location datums.
What it does need is a large enough flat face on the inside of the dropout, which your frame seems to have.
The only way to find out for sure is to bite the bullet and buy one - if, when you can offer it up, it's obvious that it won't work then sell it on and if it needs minor work to clear a weld or something then take a file to it and make it fit....