It's probably worth something inbetween those two figures!
Valuations are very difficult - you can try to find something the same on ebay and watch to see what it sells for, which would give you a rough idea. But the price something goes for depends on where it is being sold and who the audience is, and once one piece has sold, that's one potential buyer out of the picture. It also depends on market trends and the weather on the day... and what colour eyes you have...
For insurance, I would imagine
£200 would cover it generously. But I haven't a clue how scarce this particular set is, and not knowing the maker's name doesn't help.
woops! Welcome to the gmb!