- Clutch is slipping badly, think it needs a new one which I reckoned may be about £250?
You can get clutches for next to nothing, depends on what you are after but it's a home-fit diy job so prices starting from £50 for a clutch kit.
- Wheel bearing is on its way out - reckon that would be about £60 to replace?
Which wheel bearing? Front is a single unit and requires a press to push it out but again not much cost involved.  I usually remove the hub and take it down to my local scrap yard who charge £10 to press the old one out and the new one in ÂÂÂ

- Unable to put more than half tank of fuel in the car (max I have had is 33 litres and read the tank can take about 55 litres). Thought it may be some sort of blockage but have no idea how to check for this/fix it?
I can't say that I've ever really filled the tank completely so can't even estimate a guess as to what you should be able to fit in there.
- Possibly related to the above, but the fuel gauge stopped working completely today! Was showing half a tank earlier and now sits as far to the left as possible (well below empty) .Is it a knackered gauge?
It's either a loose/disconnected wire to the gauges or a knackered lift pump in the tank.  Open the boot, remove the carpet and you should see a round plastic cover over to the drivers side held in with a couple of screws.  Just remove that and you have access to the lift pump, try shorting the connector (can't remember which pins though as some are 2 pin, others are 3 pin) and check the gauge. If it still doesn't move it's a problem further down the loom and not necessarily related to the lift pump itself.  If it is the pump you'll need a pair of water pump pliers as it's a bit of a job to unscrew the pump without.
- Rattling/misfiring sound when breaking and changing down gears. Not sure if this could be the exhaust loose at the front (the backbox was replaced 2 weeks ago by me so can't be that)?
Leaking exhaust letting air into the system when/where it shouldn't causing a vapour detonation.
Regards
Ian