Hi Ronald - welcome to CC!
Too old? No - I have done 200 km audax rides and chatted to riders in their late 70s/early 80s who were way fitter than me and really enjoying their cycling. I know someone who will soon be 80 and he still races, and occasionally wins!
Too fat? No - I have met people half as big again who were cycling regularly. I got to nearly 18 stone at one point but was still riding over the huge hills we have round here. Weight doesn't make a huge difference to how hard it is to ride until you go uphill, when it certainly
does! I had a look on my OS maps and it seems that Coalville is in an undulating area. Some significant hills, but not monstrously hard ones. You will probably find them hard to start with though, but soon get used to them as you get fitter and learn to pace yourself. I'd suggest making sure that you have some pretty low gears on your bike for the climbs.
Bike for the road? Road bike! Maybe a cyclocross bike if you think that you might fancy doing some offroad riding from time to time - you could ride semi-slick tyres which are ok-ish on and offroad, or buy slicks for road rides and knobbly tyres for offroad. Better still, 2 sets of wheels, one with slicks, one with knobblies, and swap wheels according to where you will be riding.
As others have suggested, most of your hoped-for weight loss would better be achieved through controlling your diet. It takes roughly 100 miles of cycling to burn off a pound of fat so doing it purely through exercise would mean a lot of hard work!
Good luck, and enjoy your cycling ...