Does anybody know of a source in the UK of rhododendrons bred by a guy
called Kondratovics at the Univ. of Latvia? I have tried googling for
sources in the UK but come up with nothing.
TIA

No, but this link gives you names of the hybrids he's bred and other
details, but you probably know them anyway:

http://inventions.lza.lv/eng/izgudro...dratovicsR.asp

What's so special about them?

I don't know if there's anything special about the rhodos, but one of them
has the same name as me: Dace! No other reason! There's also an iris ensata
with the same name which I have located in the UK.