FWIW. Presuming that the crank is-and-has-been properly secured to the BB spindle AND that you haven't allowed the crank's receiving "mortise" to be
wallowed out by the crank
not being properly secured to the spindle, it could simply be that your BB cups need to be adjusted ...
If the crank is securely attached, then grab the NON-driveside crankarm and then try to slide BB spindle to-and-fro by pushing on the crank arm and then pulling back ...
If you can slide the BB spindle to-and-fro then
adjust the non-driveside cup by tightening it.
If you cannot slide the BB spindle to-and-fro, then go to the driveside of the crank and see if you can wiggle it by grabbing the pedal & pushing it (the peddle) to-and-fro relative to the bike's frame ...
If you can wiggle it, then see if tightening the crank bolt which is securing it to the spindle removes the wiggle.
If you tightening the crank bolt does not remove the ability to wiggle the crank, then remove bolt and see if the crank arm can be easily removed
without a crankarm remover ... if so, then you need to either replace (
!) the crank arm OR you can try to shim it with some BRASS stock.
In the worst-case-scenario, if you have damaged the crank to the point where you cannot secure it, then you do NOT have to replace the crank with another Campagnolo Triple crankset and/or BB ...
- you can certainly buy an FSA MegaExo Triple + BB cups for less than £80 on eBay ... you can probably buy a Shimano Hollowtech II Triple + BB cups for less than £100 on eBay if you are a wise shopper ...
- a "Compact" (50/34) Campagnolo-or-other-brand crankset is another option if you do not use your Granny gear ...
- OR, you can get a "Compact" crank (of any brand) + (presuming your bike has a 12-23 or possibly a 12-25 Cassette) a Cassette which has a 29t cog and/or re-stack your current Cassette with a 29t MICHE cog ...
- OR, a "standard" crankset (53/39) may be an acceptable alternative if you find that you do never use your Granny.