Depends where you are, but you could look for a specialist garden/lawnmower firm in your area, go along and actually have a look at them, see how easy you think they are to start, make sure the pace is right etc. I know a couple of places in Warrington from when i used to use mowers for work etc but sure Yell could point you in the right direction.
For me it would be Briggs & Stratton over mountfield, but that's only personal preference, though i would be more inclined to pair it with Atco mowing gear (i've used them and trust them) but that would push the budget up. Other than that, as mentioned above, I used to use Honda rotarys for the industrial estate work or pre-cutting fine lawns before using the cylinder for a final cut.