I don't see why not, Soo. You live about 20-30 miles further north than us and we grow them in an unheated greenhouse. Be careful of the overhead watering in dull, cold weather - it could encourage mildew and rotting. I think that you would be better just watering the compost directly rather than the whole plant.

Thanks, my tunnel's water system covers the whole area, and as I thought toms don't like wet leaves, which is why I am asking if anyone has successfully managed to grow them this way.

It's definitely not recommended, but I put an overhead system into my tunnel a couple of years ago and water my toms this way all the time.
Things to look out for are the leaves going mouldy as Bulbaholic says, and also the leaves scorching if you water too much in very sunny weather.
I find it best to turn on the overhead sprinklers during the early morning for just enough time to dampen the soil, and then nothing more apart from a few quick 'bursts' to dampen down and cool the place off in very hot weather.
The mould problem only really gets bad in September and October when you should be cutting right back on the watering anyway.
In the end it's a choice between spending an hour or more every day carefully handwatering, or a few seconds turning on your overhead system! Or lashing out more money on a fiddly trickle irrigation or drip system.

thanks for that, I'm going to give it a go, I usually grow them in my greenhouse and water them by hand but as I'm away a lot I thought I'd try the tunnel where at least the watering would be regular along with the other veggies. Sept and Oct shouldn't be a problem cos this far north our seasons pretty well over then. Cheers