So I've been making a couple of little changes and testing a few more bits, so here's another update!
First job was to add a (very) small bit of countertop beside the sink. Another of my skip finds!
Then I headed off camping, where I changed my mind completely about 240v electricity - very handy to have a cold fridge (and beer) on hand!
I also set about testing the cooker properly - everything seemed to work well, including the grill.
A happy chap!
I've also decided to make the whole thing a bit more "camperish" from the outside, so it fits in a bit better on the campsite, so I'll be sure to keep the forum updated with my cheesy additions(!)