There used to be motorbike parking in Arundel Street, which was the only bike bay not completely chocker when I worked around that area (before Westminster bike bay charges though). There was some on Exeter Street (but that was always full to breaking point, expect scooters jammed up against your bike) and I think some on Drury Lane. It is a while since I parked there though. I don’t envy you.
not a guidance at all but my GSR was never touched in 8 months of parking on the street in london bridge - not a desirable bike? Having said that, now I have secure parking, I would not even consider parking on the road!
Plenty of parking around there,Bedford Street,Chandos Place,William IV St,St Martins Lane in fact most of roads around Covent Garden have bike parking. Arundel St as mentioned at the other end of the Strand,plenty of places
Make sure you’re aware that you cannot leave your bike for free in bike bays in Westminster. You need to register with their pay by phone system and call up to pay when you’re there. Alternatively, cross over into a neighbouring borough where bike parking is still free and you don’t have to bother with all that hassle.
I’ve only parked in the area a few times but found it a bit of a challenge. If you get a space then you might want to wedge two large bike sized chunks of polystyrene either side of your bike!
Top tip: Central London parking bikers, in order to increase the footprint of your bike, keep it dry-ish and avoid small scratches, why not use a cheap bike cover. IT can also serve as a sheet for warmth when you are made homeless by rising petrol prices and insurance premiums!