Back in March 2016 I bought this green saddle from Amazon to put on the Boardman. Just had a look through my orders, it was £4.99!
Anyway it wasn’t especially comfortable as you can imagine. I think I did one 25 mile ride then took it off again. It’s made of fibreglass-reinforced plastic. But it is very light and I’m going to give it a go on the Planet X. It does have a bit of give in it, it’s not rigid. I might get used to it.