Not that I'm a law student or anything.

But........
indoor plants if harvested properly can make APPARENTLY, 500g, <half a kilo>

So see that as the maximum.
If your groing 6-8 plants that could theoretically be 3-4kg of weed.
If you get busted with 3-4k of weed, think cops will believe you its for personal use even if it is?

I live in the UK as well, so I know how things work here.

After you have dried out the buds and everything, if you start growing more plants, then your going to have : your already done weed, and plants.

To be honest, I don't know anyone who has been busted for growing weed, because they were all smart, except one, he filled a COMPLETE house, kitchen, bathroom, living room, 2 bedrooms etc etc.... and he got 5 years.

Weed is still illegal, even though its been downgraded to c class, and now for smoking it, most you'll likely get is a slap on the wrist and it confiscated.

However.... It's better not to get busted and grow as much as you want, rather than grow a little, get busted, then say its only 4 plants etc.

If you think your going to get busted, don't do it, thats my advice.

Mole.