I have just bought a set of Maverick clippers (they aren't Wolesley though, they are distributed by Eddie Palin) - they are the ones with the fixed tension and the head that can be rotated. Our pony has Cushings, so this time of year has to be clipped every 10 days or so and his coat is really thick. These clippers are coping with it brilliantly and don't over heat.
I bought some last year, I was just asking for opinions as I've had a few minor probs. I have several occassions where they just would not even attempt to cut and it's taken two or three attempts at cleaning and putting them back together before they work. Also the cut they give which is medium baldes doesn't seem that close - how close do yours clip?