I would get one from a caravan dealer if I were you. Microwave ovens are rated in terms of power output so a typical samll 650 watt microwave may in reality drawing well over a kilowatt. THis might well be enough to blow a fuse when added to all the other stuff you might have switched on.
A 650 watt microwave is about the smallest you'll get from either the high street retailer or your caravan accessory shop, but the prices will differ vastly.
We bought our micro from our local supermarket for
Many thanks folks, I understand the loadings of electrical supplies and will endeavour not to trip the overload. Currys do some smart looking compact units at reasonable prices.