I have decided to purchase some 17s for it, but I have a few queries!
1) Will they go on okay?
2) Will my car look like a tractor unless its lowered or is the standard set up able to cope with 17s and still look good?
1) Yes, buy some 17"s that came fitted to a later model 147, or 17"s from a 156 or GT and they will fit perfectly. Aftermarket wheel choice that fits spot on are rare to find, and I reckon its a bit dodgy to use them wobble-bolts, although many have done without problems.
2) Your car probably looks like a tractor already, most 147s do! No offense, I'm just quite used to my 156 which is absolutely slammed to the deck!
The standard set up isn't very good if you ask me. I would fit some springs that lower the car around 30mm, and also some good shocks, like Koni Sport or Bilstein. 40mm is quite a drop, combined with 17"s you might lose a bit of ride quality, but with a 30mm drop and 17"s it should be as good as it is now, if not better, and it will handle a LOT better. If you do this, consider stiffer anti-roll bars as well, these really transform the cars cornering ability too.
Right now for the bit I think is serious
It went through the service fine no problems at all, BUT I have noticed a few things
1) the coolant is dropping from max to min VERY quickly, But there's no mayo in the oil (yet) or oil in the coolant tank!
2) the car does smoke alot regardless of engine temp! is this normal?
3) there's a strange noise coming from the rear when at speed, I thought the wheel bearing, but service said bearing were all okay! what else could this be?
4) The gear stick is now not centering itself, Is this likely to be a big problem?
1) Probably a leak, head gasket failure is thankfully rare on Alfa engines provided you haven't run it low on oil. You do know the oil level needs to be checked WEEKLY, every week, without fail, and topped up if necessary? Don't wait for the low warning light to appear on the dash, by then the damage is already done. As someone else said today, the low oil warning light may as well be a big £ sign.
Now, regarding the places coolant could be leaking from.. Pipes to the radiator, or the radiator itself. Does the temperature needle ever go above 90 on the dash? Once its up to temperature it should sit just below 90, maybe creep above 90 in traffic but then the fan should quickly bring it back down. Your car is a 2002, so if its never had a radiator before I could imagine the original one is well beyond its best and leaking. Coolant loss can be hard to trace if it is dripping onto something hot and quickly boiling off.
2) Could be down to the time of year, what colour is the smoke? Black = unburnt fuel, blue = oil, white = water.
3) Don't know.
4) This is a common problem, the gear linkages can get dirty/clarted up. Cleaning them out needs the battery out, and the battery tray out, but isn't a hard job if you have basic spanner-twirling skills and a saturday spare.
Best of luck, and welcome to AO