Re: 156 to buy
Depends on Age, service history and general all round condition. If it needs a full service inc plugs, cambelt, variator etc etc then you are looking at another £600+ on top. If it hasn't got decent history then personally I would run away.
I recently bought a '98 2.0 TS Lusso for £1200 with 72k with full service history, all from Alfa dealers/Alfa Workshop in Royston.
On top of that I've spent another £330 for cambelt/balancer belts + tensioners to be done (using genuine parts) for peace of mind.