I'd locate some 1812's 4000k for the mars. One cob per driver 30ish watts each. Not sure on U.K. Pricing but here that can be owned for around $20 per cob with holder. The light will have a lot more blue but still be suitable for flowering. Another thing to remember is the amount of blue in the new light is probably double what you were using before. Those 3w diodes are no comparison. Give the cobs a shot at veg before you do anything crazy. You will be impressed that's a guarantee.
Cheers for that @BigSm0 , 4000k and citizen was what I was thinking for the cheapest option... I'm going to get new thread stared on this now.