Have you ever grown ANYTHING before?
Not cannabis but anything at all?
strawberries? Tomatoes? Geraniums? Marigolds? Sunflowers?
If you can’t even be bothered to measure rooms in your “average” British house how on earth are you going to work out everything you need to do in order to sustain this kind of operation?
As
@speedwell68 has said you realise if you’re over 9 plants (approx) that they’re gonna charge you with intent to supply along with industrial cultivation.
I got done for 4 plants and got a caution back in 2012.