I have a small tractor which is a different design from the normal. It's called an 'alpine tractor' because the people in northern Italy and Switzerland use them to cope with steep slopes and difficult terrain.
I got mine from a company in Marks Tey near Chelmsford called BSG. have a look at their web site for more detail:-
http://ww.bsgtractorsandmachinery.co.uk/epages/es109747.sf/en_GB/?ObjectPath=/Shops/es109747_shop/Categories/%22Quad%20Tractor%20Range%22Mine is a second hand machine but in good condition. BSG have been very helpful. My tractor has a 20hp air cooled 2 cylinder diesel engine. So it's fine for my 12 acre plot, it's got a category 1 three point hitch with basic hydraulics, low pressure balloon tyres tyres, differential locks on the two axles (in case it gets stuck in the mud or on a slope), and a standard power take off to operate mowers and similar devices.
I bought it because of worries about slopes and turning over. It is quite light weighing 600kg and with the fat tyres it doesn't cut tracks in the ground or cause the ground to get a hard pan - a layer of compressed soil.
The air cooled engine doesn't need any anti-freeze but you have to check that the cooling ducts round the cylinders stay clear of dust. After using the topper to cut a fine crop of thistles, I found the fan had sucked in a bucket of thistle seeds which were neatly packed round the two cylinders. Easily cleaned out and no harm done!
The engine is pretty noisy but reliable and runs happily on red diesel.
There are other alpine tractor suppliers in the UK but I can only speak about what I have.
NN