Series 3 rewire

So, during lockdown I started ordering parts left right and centre for my series 3, 2.25 petrol. Somehow I decided I had a choke warning light switch on the choke cable and ordered the a main wiring loom and corresponding engine loom from auto sparks. Which arrived after the std 4 months (now longer than that I believe). Now that I’m finally getting round to looking at the electrics, I’ve now realised I dont have the choke warning light switch fitted. (vehicle has a Webber carb and after market choke cable). Don’t know how the hell I made the mistake, but I have done. The engine loom (LR323) is to be used only with LR301 main loom with choke switch. I’m trying to find out if I can just get the correct engine loom (LR325) and fit it to 301? So annoying given the long time they took to arrive.

Will auto sparks let you exchange
Failing that will it plug into main loom , what colours don’t match/ match, work out from wiring diagram what’s affected