Just bought a MK3 L Reg 1.4 merit as a runabout till summer......what things should you check / change when you buy a used car with not much service history??

The car has done 70K miles and looks pretty clean outside, inside and under the bonnet....

Was bought form Vauxhall by a guy 5 years ago for £3500, and had a new exhaust 4 years ago - and has a 12 months MOT thats all I know!

THe only problem is when I turn the heater on sometime - usually when cold - there is a horrible loud screeching noise...... I'm told this is either then fan belt? or the "fan motor bearings" or something?

Someone said I might try squirting lubricant and/or WD40 into to bearings and this may stop it?

Where is this motor/belt in the engine bay - and what exactly are these bits called and what are the problems likely to be exactly?
And how can I solve them?
Sorry - I've no Haynes manual - and not had an astra before!!

Thanks