Hi everyone.
Many thanks for your replies.
The engine seized because I forgot to check the oil. I took the engine apart and separated the con rod from the crank after a struggle, I then managed to dig the bits of metal from the con rod, polished the crank and con rod. (I know it's not the right way to do things) anyway it felt pretty good so I put it all back together.
It runs O K and is not making any noises, did 2 hours mowing on Saturday, no problems.
I don't know how long it will last though.
I will bear in mind your 11hp B&S Stormin as I think I might need it one day.
Regards Grumps.