I'd say somewhere between manager and senior manager position. Senior, because you should have the expert skills within your funvtional area.
Not senior, because you probably do miss some UK market knowledge, do not have a high placed network (selling purposes) and maybe the way of doing business in the UK.
Not senior, because your high positions were at Charity Organisations, where - maybe- the job is differently than in the large scale private or public sector. Large scale / big companies, which in general are the clients of the top consultancy firms.
Of course, I do not know you and do not have your cv, so I might be wrong with some parts of the "not senior" reseans.
Good luck with finding the right position,