because the stud holes wont line up properly (pcd 98 / 100 ) wobbly bolts have some kind of a collar that moves 2 mm so that the bolts will seat properly they are about £20 - 30 from demon tweeks ebay pretty much anywhere that sells aftermarket alloys
probably halfords too
this next bit was written by shiny car a wiser guy than me
there's a very good chance they will fit. the only major difference is the bolt pattern: 5x100mm (5 bolts, PCD (pitch circle diameter 100mm, which is the diameter of an imaginary circle through the bolts). your 156 has a bolt pattern of 5x98mm.
to overcome this, you can use 'wobble bolts', which are bolts with a loose-fitting washer. the washers take up the extra slack to achieve a 5x100 fitment onto a 5x98 car.
the offset should be right: +35mm for an 8" wide rim. tyres are the right size to achieve a very similar 'rolling circumference' to your originals: 225/40. but there IS a chance the outer edge of the tyres rub against your wheel arch liners, especially at full lock of the front wheels or under full load/over bumps (esp at the rear).
other thing to check is the diameter of the 'centre bore' hole (aka spiggot). this is the hole in the centre of the wheel, where that 'VW' badge is. this is important, and needs to be 58.1mm to fit onto the alfa hub. this junction between wheel and hub is what takes the weight of the car, hence it's crucial (ie: the bolts do NOT take the majority of the force/weight). if the centre bore of those wheels is bigger than 58.1mm, that's not a major problem because you can buy 'bore rings' which are spacers; fit one in, and it will reduce the diameter to 58.1mm (ie: if you fit the right one!). if the bore is smaller, then it's no good unless it's redrilled to the right size (if that's possible and appropriate).
so, alfa specs on the 156 are:
*+35mm offset (give/take 3mm) for 8" rim should be ok
*centre bore 58.1mm
hence, there's a couple issues to overcome/check, if you're prepared to do that. you may want to try them on first.
he makes more sense than me