OP
Your best option is to do the City & Guilds 2346-03 Experienced Worker NVQ Level 3, it should be easy to do on what you are saying and can be rattled off in no time.
This is what Napit suggested and I have considered it. But being temporarily out of the industry would make it difficult to get the evidence for the portfolio. As I mentioned earlier there are a couple of things within the scope that I haven't got previous evidence to draw on as there more commercial installation and I've been almost entirely domestic.