Cost-wise, I'd consider adding commuting cost to your hourly flying rate. I commute from London to the gliding club I fly at, it takes a couple of hours (by car or public transport). I believe the easiest places for public transport are Booker, Denham, Headcorn, White Waltham and for microlights, Damyns Hall. I wouldn't buy a car specifically for getting to an airfield though.
You could fly on microlights though you'd need to convert from a microlight NPPL to an aeroplane NPPL. You may want to consider whether your instructor is qualified to teach the JAA PPL if you go down this route as this may have an effect on your training. I think renting microlights can be difficult, I think you may need to purchase a share in one post-licence acquisition.
Safety-wise, as one magazine said "if it reeks of oil and the wheels shimmy like those of a shopping trolley, don't risk it". I'd consider the state of the aircraft, the instruction you're receiving etc. though the PPL folk will know more than I do.
I generally fly gliders once a fortnight and that is often enough for me, though I'll spend an entire day at the airfield and fly 2-3 times, gliding does tend to be fairly social and I do pitch in with launching/retrieving etc.
If you're flying March-October, wear plenty of sun-cream and/or long sleeves, Perspex canopies offer pretty much zero UV protection and you don't want to get basted.