My Stanley Gibbons catalogue  pages for this are missing. I never noticed and now it is too late to complain. But I have used Stamp World, the brilliant on line catalogue. Use it if you have not yet! https://www.stampworld.com/en It  is an absolutely brilliant and free reesource. Its prices are very close to Gibbons.  Even though it is free, I donate and if you use  I encourage you to do so also. It is run by a bunch of enthusiasts and I cannot fault it. Oh, hang on. I did find they missed out a few existing stamps, But I wrote and they have now included them. Wonderful resource that needs to be more used and contrubuted to. It could put SG catalogues to the rubbish box of history! Not something I want but their catalogues now miss out thousands of legitimate stamps while putting in a lot of the Royal Fail [sic] rubbish that ought not to be listed. Why? Because now Royal Fail stamps are not on sale to the public and Royal Fail does not want anyone to actually use them. But back to these stamps.
Stamp World values these at 5.50 - which is about £5. I start the bidding at one fifth of that. By the way, the scan of the backs of the stamps shows the two at the bottom being slightly yellow. I can assure you that all four are perfect and white with no marks. My scanner is very good but sometimes when there is little to be seen it had a mind of its own and adds colours that are really not there. I tried several times to get it to see sense. But machines can be stubborn! This is a lovely set - and Yes, it is a set - all being issued on the same day and all together as if one set. The Irish Post Office is very lovable and funny at times.  Why not link Children's games, the Red Cross and European Elections? Makes sense in a kinda Irish way.