In the UK you're not only allowed to take the whole lane, the Department for Transport (through Bikeability) calls this the primary road position for cyclists. The guidance is that this should be the default, with the secondary position (~1m to the left) only used when the road is wide and the rider is certain that keeping to the left wouldn't compromise their safety.

https://www.britishcycling.org.uk/cycletraining/article/ct20...