In reply to Tom Purnell:
Generally grades indoors aren't worth the chalk or ink they're written on. Some of them get round this by making their own system up or using british tech grades.
There're a few walls that I would expect have their grades sorted, The School, Boulder UK, (maybe even Nottingham?)
The hardest problems at SCUIBL were probably around 7a+, give or take a grade. Nudging in to english 6c (boulder) maybe.
Have you not bouldered outside much? You might well get spanked at first but you would probably be able to find a Font 7a+/7b you could climb. Maybe even Font 7b+ if you put the (days of) effort in. Soft 7c if you really got into it.
Isn't the obvious next step BUSA? They usually have one or two harder problems than SCUIBL.
I would've thought the problems in the finals of the BBC are set around the font 7b - 7c(+ or harder?) mark.