would this toilet seat http://www.next.co.uk/x5d4350s5 fit this toilet http://www.wickes.co.uk/Portland-Toilet-To-Go/p/223115

In USA, we order toilets and toilet seats as follows:

A ROUND toilet seat will fit a ROUND toilet bowl. An ELONGATED toilet seat will fit an elongated toilet bowl. You'll find your best fit keeping manufacturers of both the seat and the toilet the same... ;)

In your case, it looks like the toilet seat will work with the chosen bowl, but since the toilet you choose comes with the toilet seat I couldn't find a clear distinction on elongated VS round. I would call the customer service department at both sites and be sure you match up to be sure!

Mark

I agree, the seat and toilet both appear to be round and not elongated

Look on the toilet bowl for the manufacturer name on top of the bowl behind the seat bolts. Then contact that party for the correct size.
Good luck, Tom