score:6
If it is no bike rack, with or without signs you can expect your bike to be unwelcome.
They will not remove bikes in all locations but any place which is not an official bike rack can be seen as 'no bikes here'.
As there are not enough bike racks in most places, (not just London, not just the UK but everywhere bikes are popular,) you may have to park your bike in an unofficial place at times.
If it is just for a few minutes you can get away with a lot more than if it is for a day.
If you need to leave your bike for a long time, search on till you do find an official rack or a bike parking.