Adam, very sorry to hear about BW engine
Dont panic mate
If I were you with 1 day to the Southampton boat show I would go and check the prices.
new engines are heavily discounted at the show, and come with all the bits required so are an easy job to fit.
If you got an update of your present engine it may be even easier to fit as the old control box and cables would do the job, and the new ones could be added later. also all the holes in BW would be in the right place.
Check out the specs and the prices, ask the dealers about any old stock units they may have.
They would be new but dated as last year or older, and the price should reflect that.
I would not go the repair route if it were me. but I would shop around on the net and visit the show.
very best of luck,
if you need advice or help to fit call
Charlie