The circling aircraft was actually holding on the NDB which is on the field at London City. Alkin is out in North Kent, and as suggested above was likely already full.
Back to the fate of certain 146s, supposedly more my area of knowledge. Of the four Air Malta aircraft one is now operated for SAS by Transwede and can be seen at LCY daily on the Stockholm flight, another got fitted out for VIP work in the Middle East, and the two that passed through Euromanx's hands (and on one of which I once enjoyed a shambolic journey from LCY to the Isle of Man) continue to have bad luck as they were taken by an Italian independent which more recently has ceased operating so they are once more laid up, at Exeter, and thus presumably up for grabs.
But an RJ70 is such a small, niche market aircraft. Helsinki (speaking as one who has been there and finds it has a nice airport but is otherwise a rather simplistic little city) is not THAT strong a financial business market so you would need business in the Y cabin as well. And just because the RJ70 could do Malta to Dusseldorf, both with 10,000 foot runways, wouldn't necessarily mean it could lift out of LCY the same.