Just to pick up on Tom's point about discounting. This has been the main reason why I have never seriously considered becoming a testing station.
I have been watching the m.o.t. computerization fiasco as it's been unfolding over the last year or so. To be honest I thought this could finally be the right time to get a test station and make some money.
Unfortunately though the muppets near me have already started cutting each others throats! The cheapest near me (for now) charges £35.00 and no retest fee, mind you as far as I know it's trade only for free retests. There is another station though only 3 miles away that is doing the same for £25.00!

Don't get me wrong if the chance came along to take over a testing station near by for the right price I would be tempted but I wouldn't see it as a huge profit making decision. It would just make my working day a bit easier and save me some time.

In my opinion unless you have or can get:-
(a) a good relationship with your "testing" neighbors and you all agree to stick to a fixed price.
(b) a very high volume station.
(c) an assurance that v.o.s.a. will finally do what they should have done years ago and make it a non-discountable fee.

I would be very careful and do your sums before diving in at the deep end, all you need is one or two arsehole's near by and they could scupper your hopes. The majority of the public (bless them) are only interested in one thing,"WHO IS THE CHEAPEST"

Just my thoughts,
Cheers,
John.