it depends where in the uk you are! scots law and english law are two different things.
it would also depend what else was found in your house,if you've got a roll of baggies next to your stash,youre getting done with "concerned in the supply"
The Misuse of Drugs Act, 1971. Section 4(3).
worst case senario you're getting done with "drug production"
The Misuse of Drugs Act, 1971. Section 4(2).
but as with all court cases its how good your lawyer is,and what,if anything else is found in your house. and an important point,in the uk,they take how sophisticated your grow operation is,its easyer for the prosecution to make your hydro setup sound like a sinister thing and portray you as some sort of ganja scientest,when if fact its just a couple of nft trays!
if youve no previous convictions,a clean house (ie no other drugs,tick lists etc) and just 6 plants,i think you would get a suspended sentence,or worst case probation and a fine/community service.
dont tell anyone that youre growing!! "loose lips,sink ships"
be safe,and i hope you never find out the exact answer to you question!