Just for anyone who may be browsing in the future to do this job - the space in there is really limited so I used the damaged bolt removers linked below - worth their weight in gold imo. Tapped the 13mm on the bottom bolt with a long extension bar and got one of my aviator spanners on it - bingo. I gave the caliper a few knocks up and down with a lump hammer to break the seal on the top bolt then put the same bolt remover on and got at it with a 19mm open ender. Couple of hits with the lump hammer and she was free. Need a vice to get the bolt out of the extractor due to the lip on the bolt - the kit comes with a bar to knock em out. Hope this helps someone in the future...
https://www.amazon.co.uk/Reelva-Dama.../dp/B01N8PEJIF