First one I've got (lightweight bodywork, spray glued a cut up camping roll mat but this is one area I missed), its about the size of a 5p piece (or smaller).

Caused from the inside from a stone flicking up on a track day.

I'm worried that I'll catch it when using a sponge or cloth (and pull a chunk of the gelcoat off with it) so would it be a good idea to "seal" it with some clear nail varnish or similar (on the outside)?

Anyone done anything similar?

If I want to remove the "repair" at any point I guess I could do it with acetone.

acetone is also a handy solvent for fibreglass. not sure what it does to gel coat.

if its just a small crack, i doubt a sponge will break any off though

If it's a star crack and it's only in the gel coat you should be okay. The gel coat stays relatively tacky and fluid so should self-seal to an extent....

To repair it properly you'ld need to gouge out a whole load then make up a repair mix (with flowcoat not topcoat) and put in place, then sand down the buff to a fine polish...

Where is the stonechip? inside the wheel arches? i presume the cutup rollmat is on the inside of the arches to prevent damage from the inside? i have been thinking about what to do to prevent things like this from happening. ill have to get myself to millets for a look around hehe

Yeah the stone chip is right at the back edge of the rear wheel arch. I think the mat I cut up (from Tesco's originally) has done a good job but one roll wasn't quite enough (there is quite a lot of bodywork on the Fury).

I'll finish it off with another one when I get chance to buy one. Used an entire can of spray glue to stick it on but it still adds hardly any weight.