It’s a straight-forward majority vote. If you’ve got the money, pend it (but wisely). I don’t know if a small scheme is even legally obliged to get more than one quote – but it does make a lot of sense to do so. However, just to protect yourself, have a proper meeting with an agenda outlining the work proposed etc, a couple of quotes if you can get them and formally agree to go ahead, minuting the result. That way there can be no comeback from the penny-pinching third neighbour.