Dan:
Many of your questions have been answered but to address a few specific points, the smallest aircraft (SEP rather than microlight) is likely to be a single seater. For these you need a tailwheel sign off and also to get a few additional hours before contemplating buying. Many cheap group aircraft, which will be on a permit, will also be tailwheel.
Permit share are often quite cheap - in the order of £1500 to £3500 and the hourly rate will come in way below a C of A aircraft. You won't find a non equity permit aircraft as the non equity concept is essentially hire for reward, which you cannot do on a Permit. A single seat will cost you £6k to £8k outright and is the cheapest option for outright ownership.
Two hours a month in a C172 probably equates to around £300. For that money you could get say around 8 hours in a Piper L4 cub! So, the savings with a permit aircraft can be significant, though you will generally have to add in a monthly contribution. I suggest scanning the adverts in the flying magazines and on Afors.com as this will give you an idea of availability and the relative costs of different types of aircraft. Ultimately though your choice will be determined by what is available in you local (ie around 1 hour's drive) area.