With alloys condition is king, so some pictures might help, guess pescaras are rarer than monza II's, but good powder coated versions (RedRobins fine examples) havent yet sold for £600 with tyres, and some Huffs in basically perfect un-used condition havent gone for £800 which are rarer than pescaras.
So some pics might help, also might get you an offer or two...... but £500 mark with decent rubber and good condition would seem a reasonable price, and if they are good conti's maybe push £600. especially if you think that a decent set of tyres on there own will be 250-300.