Hi again delta, no worries!
Interesting... You describe precisely how I feel about the way my car feels... If you know what I mean! Even the varying braking amounts, which although I had noticed, I hadn't noticed (err, if you know what I mean again!) Strange, though the car has never "scared" me and I know the ABS works a treat!
Deffo get that waterpump changed they are only £30ish from GSF. A small price really for peace of mind. I've never touched the engine mounts on my car but i guess just lifting the block up with a crane will allow you enough access to do all of them. Just guessing here, maybe one of the other chaps 'round these parts knows better?
Back to the HG leak - are there deposits down the front of the engine, behind the exhaust manifold heat shield? They may look a bit like lime-scaly deposits you find in a kettle. These are the crystalline deposists left by anti-freeze. Another sure sign of a HG fail down the front of the block. The engine may well run OK for a while in this state, but sooner rather than later is the best policy I think. Otherwise you'll end up with the same running like a pig/annoying heater noise/clouds of steam from exhuast and eventually almost-dead car like I did.
All I can say really is that I recommend these old cars to anyone that requires a vehicle of this size. Aside from these head gasket "issues" the car has practically cost nothing to run. Aside from a cat-converter for the last MOT it has flewn through the last 4 MOTs with no trouble. Its a dead easy car to service and repair yourself too.
A good friend of mine has an Audi A4 which, (apparently) costs around £400 a year to service. Having had a nose around his car I must say I would be rather reluctant to service it myself, and is one of the reasons why I havenm't bought myself a newer car (aside from the costs, of course). He's just had a scary list of imminent "jobs to do" from the garage on the car that'll cost around a grand, eep! Suddenly a couple of hundred notes for the head gasket job doesn't seem too bad after all!
Whew, after all that, I hope all goes well with the car for you, good luck! And a Happy New Year to you, and evryone else on RenaultForums!