Am I right in thinking the inlet needs to be removed when cambelt is done?
MAF sensor seems fine just cleaned it map sensor could do with a clean but may just buy new as they get brittle
I drive my car quite hard now and then
No, the inlet manifold doesn't need to be removed to do the cambelt.
If you wanted to remove the inlet manifold, doing it at the same time as a cambelt change would save you a bit of labour compared to doing both jobs individually but other than that they are unrelated.
Unless the engine had an EGR delete when it was brand new, to some extent the inlet manifold will be clogged up now with the oil/soot mix aka the black death. A little bit of clogging won't cause errors but if things are well clogged up then it will cause running issues like the ones mentioned.
I don't think driving it hard will clear it out at all, my karcher pressure washer doesn't get it all off at point blank range, sometimes I have to resort to scraping the rest of it off.