One of services we have always offered is freelance Umbraco website support, even for sites we did not build.
This is where we differ from other agencies in that most will only support the sites they built (and some won't even want to do anything past the initial build phase!).
We have a few options for you from fixed monthly support hours to flexible retained hours on a monthly basis.
We're based in Llandudno North Wales but support all of the UK.