Amazing pictures!
It belongs to the Chrysidini and not Elampini (like Hedychridium), the habitus is too slender, the last tergite has a transverse row of pits (sometimes missing in Chrysidini but never present in Elampini) and the radial vein too long.
The radial vein ends a bit away from the wing margin though, which together with the evenly rounded last tergite and dense puncuation makes me sure its a Pseudospinolia. According to fauna europea there is only two species in this genus in the Czech republic, P. neglecta and P. uniformis, the former is differently coloured so this should be Pseudospinolia neglecta (Shuckard, 1837).
It is a bit strangely coloured, but maybe there is some variation in this species. I'm used to them being pure red on the gaster and blue/green on the thorax and head, the "off-colours" on this specimen are very pretty, but perhaps nothing uncommon, Paolo will certainly know
/Alex