[verdverm]

Sounds like you are getting bad vibes and you should either talk to A and get proper employment or walk away and find a gig that respects you. If company A really wants you, they would do the right thing.

Umbrella company is a tactic that seems to be growing which uses corporate legal resources to increasingly take advantage of people. The insurance part is normal, the rest smells of asymmetric knowledge and positioning. Typically as a contractor, you have the ability to reuse your skills without restriction. If a company wants to restrict that, they work it into the contract and should provide ample compensation. Contractors and consultants typically have specialized skills. A non-compete would typically have an industry or technology as the determining factor, not that the other companies do business.

tl;dr it smells and you are probably only getting the first whiffs.