Could anyone tell me of a good make, and strong make of 20 inch or above uni?
I’m 15 stone, so don’t want a cheap one, that will break etc. Cheers for any feedback 
There’s quite a few available. The question is: what is your budget?
The people at unicycle.uk.com are very helpful and there is a lot of info on their website. They have a deal on the 24" Nimbus this week as well, which might be ideal for you. No connection, just a happy customer. I’ve got the 20" Nimbus.
Can’t beat the value for dollar on the Nimbus II. Pretty much indestructible for a basic uni. http://www.unicycle.uk.com/unicycles/adult-learner/nimbus-unicycles/20-nimbus-ii-unicycle-black.html
48 spokes, steel frame, tough as nails for beginner riding, comes in a few different sizes.
I don’t really have a budget. I have a very cheap 20 inch, I’m learning to idil on. And have a 20 plus year old 28 inch uni, with the old cotter pins on pedals.
My aim is to get really good at idling, free mounting and riding backwards on the 20 inch then start using my 28 inch, to then do all I’ve learnt on tthe 20 inch uni.To then get a decent 29 inch uni for road.
Don’t forget you’ll also need a 26” muni for razzing around Delamere Forest etc,etc. 
The 24" unicycle from unicycle.com.uk looks great !
Like the Nimbus, the Qu-Ax Profi has a 48 spoke double wall rim with an ISIS hub. I think the Nimbus cranks are stronger though.