I've done a quick search but couldn't find an answer to this question.

I'm thinking of how I'm gonna sort the pedals out and thought about using a pair of "L" shaped brackets back to back welded to the floor of the car to hold each pedal. Does anyone foresee a problem with this? Would SVA man approve?

If I understand you correctly I think you may have underestimated the stress that can be exerted on a brake pedal (especially when that bloke in front slams on his brakes )

The master cylinder takes quite a beating sometimes and needs to be braced between a couple of sturdy cross members to avoid flexing so the pedals will need to be mounted equally strongly.

If you made the brackets like that but deeper, and then notched them at the back to step over the chassis tube, then welded the "L" to the floor and welded the rest of the edge over the chassis tube and to the bulkhead plate then that would be plenty strong enough.