Anyone knows a place for Cycle Servicing, Modifications and Electric Conversion ?

Hello, I have an extremely old bicycle which I need to get repaired, modified to bit of fatter / hybrid tires, add gears and convert to electric. The reason is, that the frame of my cycle is larger and no electric bicycle offers a large frame, so modification is the only way. Anyone knows a place who can reliably get it done without creating a hassle ? Before you answer, note that I have tried talking to all famous places (without naming, the places at Meadows, Bramhand and more), and they all refused or created unnecessary hassles.