I am having finish issues on my pattern and mould when using Unimold gelcoat. The first time the part was finished in clear lacquer form Halfords. The part was easy leased and then waxed 8 times. When de-moulded the finish on the part had alligatored leaving a poor quality mould. The second time had 2k lacquer finish, again easy lease and wax with the same result.

*edit* sorry, misread your post. 

The problems sound to be in the preparation of the plug rather than the release agent or the Uni Mould.
The styrene in the Halfords rattle can clear will have caused the problems on the first mould. My guess is you tried to correct that on the second attempt by using 2k clear. 2k can take weeks to fully cure at low/ambient temperatures. If you try to pull the mould too soon the heat generated during the exotherm will soften the 2k which can cause surface finish and release problems

Using an Epoxy gelcoat is an expensive way of trying to fix the problem. You will have to use epoxy resin and either powder pound CSM or E glass for the backing layers. Even then the heat during curing will soften the 2k if its not fully cured.

How you apply the gelcoat also matters. Apply it too thick or add a second coat too soon and it will contract during curing, again causing problems.
If you get the plug prep right a semi perm release agent and correctly applied Uni Mould works fine, I use it all the time.

Warren

Carbon Copies Ltd

So what finish do you suggest? I now have to sand and prep my plug again and need to apply a finish.

its a guitar body - or rather the top of the body (the lower part is the other half of the mould) I intend to lay carbon fibre, reinforcement and vacuum using epoxy resin - no pre-preg or ovens will be used.

So infusion or wet-lay? 

I am going to wet lay initially and try infusion at a later date. If I don't have the time to wait for 2k to fully cure what finish for the plug would you suggest. PVA is ok as the final product will be lacquered, blocked and polished.

If time is the issue and surface finish isn't critical then PVA as Hanaldo suggests. It will need to be spray applied. That way you can apply several coats creating a decent barrier layer between the plug and gelcoat. 

I have to agree with Warren here.  PVA seems the best way to go as time is critical in your case.  In an ideal world, aim for a perfect plug leaving minimal work to achieve a perfect mould.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant