Been with Scottish Widows for many years as a customer and never once had call to regret my decision.
The staff are excellent: all UK based, all easily accessible through a short automated 'phone service. Interest rates are more than acceptable - never the lowest of the low but you get what you pay for.
Communications are always quick and efficient. You get exactly the information required and actions are swift and professional.
I sometimes have a look around to see what I would save by switching. Saving £20 a month but losing the efficient Widows service would be a step backwards for me, so we have stayed put to date. I can't see that changing.