A further carb strip down, and I noticed a blockage in the carb jet as shown. Cleared with wire, carb cleaner and air line to make sure. Also, a small bit of crud still in one of the side jets of the float bowl fixing bolt. My 'thorough' clean was not thorough enough, obviously.. Runs really sweet now.. Thanks for your help.
Cheers, Paul

Hi, again, a very good point.. Will check asap. Thanks! 

Hi, new fuel and still won't start. Stripped and cleaned the carb thoroughly again. Will fire up with a squirt of 'Easy Start' for second, and then dies.. I notice the (new) spark plug is quite oily and smelly. Is a head gasket failing an option?
Thank you! Paul

P.S. I haven't used the mower for about 2-3 years.

Hi Mick, I checked the OPC cable for slack etc. All seems ok. Will drain the fuel and replace with new. Maybe existing fuel can contents are not as fresh as I thought..  Thanks again, Paul 

Hello Mick and thank you. Very good point. I have not tried pulling on the OPC cable {had to look up what that is..}. Will try that tomorrow.

All the best, Paul

Hello all, Newbie here.. I have a 2010 Hayter Motif 41. Has been a really good mower, but recently won't start. I have stripped the carb and cleaned with an airline etc. Fuel getting through, new spark plug, clean fuel. It fires up strong and dies straight away, as before. Any ideas? Thanks! Paul