I think a day only pilot would be about as useful as a chocolate teapot to an airline, so the chances of having any sort of career in the UK are practically zero unless you can pass the CAD test.
You might get work like me as a flying instructor, but you don't need a CPL or any sort of instrument qualification to do that. And you certainly can't call it a career, since the pay is so low - I am living on my pension from my previous "proper" job and any income I get as an FI is more than offset by expenses.
Still worthwhile doing the IMC (or IRR as it is now called) as it will make you a better pilot, but just fly for fun. Or move to Australia