I have the equipment to properly grind both the ends and flutes of end mills. Unfortunately I am in the US so it is impractical for me to offer services. Were I closer to you I would propose a mill sharpening party where you bring your cutters plus pizza and beer. Maybe you can find a member in the UK that is properly equipped and willing to do a similar thing.
I think you will find the industrial sharpening services expensive unless you have a large number of identical mills to sharpen.