Hi Sarah.
First of all welcome to the world of carvanning.
Yes you can use houshold electrical items in your caravan, but you do have to watch how many watts of power you use. Typically a household kettle uses 3'000 watts to boil water which is over the ampage for a 10 amp hook up which is the common uk size. On some sites you do get 16 amps and that size is becoming more frequent these days. (I'm keeping the info simple as I guess you and your OH are not electricians).
For a kettle all you need to do is avoid any that say fast boil on the blurb, and go for a 1800 watt power one. You will find a data lable on the base of the kettle that states wattage.
As for any other appliances just aim to keep them below 2000Watts or 2Kw power and your should be fine in the uk.
Now all you have to do is a bit of basic maths. First of all, keeping it simple, 5amps of hook up = 1000watts or 1Kw of power. So a 1800 Watt kettle - 10 amps. Or kettle only on 10 amp hook ups, but if you have 16 amps to use you can use kettle + small microwave or George Foreman grill.
Sure you'll blow the trip occassionally we all do. I've been caravanning 28 years and still do it a couple of times a year. But as you get wiser, you blow trips less often. One tip would be to use the kettle on it's own, and mix the other power users.
A fan heater is usually a 2 stage unit, each heat setting being 1'000 watts.
One final item you do need to get a low power one of is, a toaster. Again you can find ones under 2'000 watts but you have to read the labels.
Happy hunting in Curry's, Argos, Comet and all the DIY's for the low power options.
Atb Steve L.