Not wonderfully cheap but...
I use a Sykes Pickavant ACR system. I bought all of mine 2nd hand. I use an ACR2 handset (30055000), Fiat2V2 pod (30350900) and a Fiat lead (30212600) for my 2.0 16v. The Fiat1 and Fiat2v2 pods cover just about every Fiat/Alfa/Lancia engine to about 2001.
If you shop around a bit you should be able to get a system for under £100. Not as cheap as a PC based OBD2 system though. Early 155s had a flash code system, 156s have EOBD I think, but late 155s are dedicated diagnostic reader only.