Update:
Bushtoy & Charles Y,
Many thanks to you both as your suggestions seem to have hit the nail on the head. I did inspect the needle valve & seat, they looked ok. then I lowered the float closure height by about 2mm. Had to readjust the idle speed and mixture and have had no evidence of warm restart flooding since, infact the old girl seems to have found a bit more umph and flies along better than ever.The money saved in petrol worth more than a couple of beers I think !
Many thanks for your constructive advice