I was wondering if it may be a bit 'crackly noisy'.... i have a 3m square cotton canvas. so i could always use the poles and have it like the ridge type shelters that are about. we shall have to see if it bothers us much
If you are using EHU then a convertor (plugs in the hookup and has a cigarette lighter type socket on the front) is really useful for a thermoelectric coolbox if you are having one. If you have more items with a cigarette lighter type plug (which we do) then you can get an adaptor that plugs in the convertor. One plug into the convertor and three cigarette lighter type sockets on the front. Very useful (or might be if you use items that have these sort of connectors).
Don't forget ice packs, a basic First Aid Kit, a basic sewing kit (you'd be surprised) and a torch.
An essential as far as I am concerned, dependant on the time of year you are camping, is citronella candles. They do big ones in large glass containers. They are useful for when you are eating outside and I have also found them safe to use in the tent because of their large glass container. Obviously, ensure they are not anywhere they can be knocked over and don't leave them unsupervised and they must be extinguished before you go to bed.
If nobody else has mentioned one (looked but didn't see a posting) then a bbq too. There are lots now that totally flatten so one needn't take up space.
If your going in March then hot water bottles are a good idea, you can even cuddle them in the evening if your not taking any other heating and just refill before bed.
Don't forget a tin and bottle opener.
Take as much bedding as you can, sleeping bags with a quilt from home, it can be really really cold at night even if its nice in the day and make sure you insulate underneath as well, speaking from experience, nearly froze the first few times I went camping early in the year, now as warm as toast.
We had much of what you did but when we went camping for first time last year didnt have hookup and managed fine. Our coolbox was just a normal one and kept things cold for a good few days with some ice packs in. We didnt have a portable toilet but the place we went their toilets were a state and our tent does have a back and front porch so room for a portable toilet and I think Ill take one next time as it saves midnight trips into the cold to go to a filthy toilet.
Also have you considered a tent carpet. Our main area when lounging was much nicer with a tent carpet. Only for the main area, not for the bedrooms.