I don't understand how the OP intends to pay themselves. 
If they are billing through this company that they only own 50% of the shares of, then as far as I can see the only options are to pay salary which would be subject to all the same taxes as using the umbrella, or pay themselves dividends - 50% of which will have to go to the other shareholder(s).
How would they be any better off?

If they are billing through this company that they only own 50% of the shares of, then as far as I can see the only options are to pay salary which would be subject to all the same taxes as using the umbrella, or pay themselves dividends - 50% of which will have to go to the other shareholder(s).
How would they be any better off?
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