I have fitted my front footwells/bulkhead. I have only stitch welded this and there is a small gap all the way round of approx 1-2mm (except where the weld is) as I fitted it inside the box section. Does this need to be fully welded to make a fire proof seal or can I put some silicon or something round it just to keep it water tight later?

no, you can use just silicon

if you look at many 7's they are totally open above the pedal box area, but you raise a valid point. My main concern would be petrol leaking into the footwell area rather than flames burning you through a 2mm gap.

So you can have it open above the pedal box for all the tests can you?
I was wondering about that and whether or not i would have to box it in.

Strangely I don't think it’s an issue but I wait to be corrected. Fire rating for cars is very low anyway, ever burned a grp bonnet? I have surprised Greenpeace didn't appear with in their rubber dingy and an extinguisher

personally I'd rather have the bonnet and footwells lined in ceramic blanket but then folk would moan about the weight...

I would think of grey Stripe Seam Sealer. Much better than Silicone. Doesnt give off acetic acid when curing (as with bathroom type sealants).
I would still seal it up. Even a burst rad pipe and boiling water on your feet isnt much fun, letalone buring petrol.

Seal up the area even if its just for safety reasons.

You Know it makes sense.