1.8 Kjet fluffing after hot start

Hi guys,
Developed a niggle yesterday that has never happened before..car has always had plenty of oomph at any temperature but went for a run yesterday.about 25 miles or so..no probs at all until setting off for home about 20 minutes later..As I was pulling off it seemed to struggle/fluff at lower revs..was fine whilst rolling but really didn't like a bootful in any gear..especially the lower 3.
Had a quick look round this morning and nipped up a few earths,cleaned plugs and stuff and went for a run of about 6 miles with no issues….about 10 minutes later struck him up again and set off down road…as bad as yesterday!
Obviously something is being affected by the heat build up after switching off..wondered if anybody else has had the same? As I say,have had car for nearly 17 months and ran/abused as a daily with no similar issues at all….car will idle perfectly and doesn't seem to fluff when operating throttle cable manually…only does it under load….
Thanks..Scott