8.5 is about right. Your car is very likely standard. Actually 0-60 in in 8.5 seconds is pretty good going for a car that age (unless you mean 0-60 km/h?
) and you'll struggle to find many mainstream cars much quicker than that, even today. The car feels quick because it's torquey for the weight. But 0-60 is for the Saxo boys.. a 146 should be above such hooliganism.
If your windscreen wipers are "small and hopeless", I would buy new ones the right size. Check the sweep of the wipers on the windscreen - if it's nowhere near the top of the windscreen then find out what the right size wipers should be (I'd have to go measure mine to tell you..
) and get new ones that size.
I'm guessing that your wipers have some play in them and the previous owner bought shorter heads so that the wipers didn't touch the bodywork. When you get new heads, remove both the entire arms and re-fit them so that the wiper blades lie on top of the little black circles on the bottom of the windscreen.. or better still, 1 notch below that. You'll see what I mean when you look. Then they shouldn't touch the body at full sweep.
The wipers should move freely (otherwise it's the "grease on the contacts" problem).. but if by "rubbish" you mean they just don't clear the water.. get new blades.. simple as that. Wiper rubbers only last 12 months.
"£25 for 70 miles" fuel consupmption might be terrific if you paid £25 per gallon. We need to know how many gallons (or at least litres) that was. Your car should do 30mpg minimum (though not at the same time as 0-60 in 8.5s
) and maybe up to 35mpg. If it likes a drink then check the thermostat.
The car should quickly get to just under half way on the temperature gauge (marked either "80" or "90" depending what age it is) and stay there, unless you're stationary in traffic. If it loiters only 1/3 or 1/4 of the way up then you need a new thermostat. A new thermostat will give you 3mpg easy.. so it pays for itself in no time.
Thermostats can be from £60 - £90 depending on the type (there are 2 different types). Try shop4parts.co.uk though. They have a discount on at the moment (£40-£50) and you can see a picture of each type, so you order the one with the shape of bottom-connector you need. No the cheaper 'stat doesn't fit if your car has the dearer one..
If the idle is lumpy or "hunts", then your lambda sensor could be on the way out. The car would drink the benzina then... since it over-fuels to stop itself stalling when it doesn't know what's going on down there in the exhaust pipe.
A new lambada is from £40 - £90 depending where you get it (avoid the £20 connector-less cheapos from fleaBay unless you like swapping them every 12 months).
An "NTK" brand.. from the 'Bay... is made by NGK (Japanese
) and has the connectors attached (so you don't have to splice in/re-use your old ones). It's around £40 and will last years.. so it's a good option.