Im in the UK too,beaves.I think British customs have a lot more bigger fish to catch,and there is probably nothing to worry about.
But to be on the safe side only grow 2 or 3 plants,and if the filth do raid ya,yer only growing for personal use,not 4 monetary gain.
If you have no previous form for drugs,you will get a small fine,£100 maybe,and your grow gear confiscated.If you have previous
convictions,you will probably get the jail,Parkhurst will be the nearest to you on the IOW.
Personally,i dnt think customs will grass on you.I get my seeds from English seedbank,justfeminised,they are ok.
Good luck pal.