Baggs, tanith and MiniMoon are bang on the money, it's a Ceanothus. I also agree that dwarf varieties are suitable for pots. We used to have a Ceanothus in our garden but after about six years it became unhappy, I think we must have done something wrong ?.
baggs whatever this flower is it’s really beautiful enjoy i had a walk down my garden path today for the first time in a year looking at all the shrubs my DH Planted quite early on which we thought had perished with the late frost I’ll send you photos when they have blossomed