Hi,
Interesting thread this, I had a .22 280k for a while, was an absolute dog out the box, shot like a mule with no lube at all. Once cleaned, kit installed, detuned to 10.5ft lbs and t06 trigger adjusted (lovely trigger to be fair) it shot ok, not cheap though. Sadly for me, the stock was terrible, the length of pull is too long and design is poor. I bought a .22 hw99 as a direct comparison and with a drop in kit it shot the 280k out the park and was cheaper, so moved the 280k on.
shame they never developed the design really, the marketing and business side of Diana RWS has always baffled me, so many missed opportunities or they're just not bothered with the UK market. The shop down the road from me in mid 90s always advertised the 52 in the window, wish I'd bought one at the time.