Advice on fin?

[Jack93]

Hi, I've been on minoxidil (5% Rogaine foam) for about a year now. In that time I have noticed my hair getting thicker and the hair loss has stopped (no hair on pillow anymore or MPB itch), but I haven't seen much, if any regrowth. I'm 20, started at around NW2. No pics unfortunately.

I'm unhappy with my hair and want to start on fin to see if I can get any regrowth/ it's easier than applying minox but I have some questions:

Where is the best place to get it in the UK? I've been looking at 5mg from inhousepharmacy.biz, is that legit?
I'm still growing, could fin mess that up?
Should I taper on? Or just go straight on to 1.25mg a day?

Thanks