Yes, I've had this all year with 5 yr old ds.
Mind you, he doesn't start proper school until September, when he'll start Year 1. He's still in a sort of nursery situation, which I think he's outgrown, even though he's in the "reception" class there.
I handled his reluctance by going with it. I decreased his days from full-days to half days and decided to home school him, informally, in the afternoons. We went to museums or movies or stayed home and did work books or practiced letters or read. I figured he'd be in school forever, so I might as well give him a little break right now. This term he goes 2 full days a week and 3 half days. In the summer I'll up it to 5 full days, as recommended by the principal.
I just think too much is expected of them at too young an age. In the US, where I come from, even Year 1 (kindergarten) is not a full day, let alone reception (preschool).
This was one battle I was willing to give in to, because, IMO, ds was right.
My way of handling probably won't be an option for you, velcrobott, by I mention it anyway.