I got my power fc for under £400 then there'll be mapping estimate another £400,
£800 all in is not bad for a stand alone and I would personally go that route as it'll will always be safer, not saying piggyback are useless but I would think a lot less realiable and worse for your engine when your only saving £3-400 pounds.
I'd say peace of mind is worth the little extra and also gives you more options for future mods where-as you would prob need a new piggyback altogether if you were to add more mods
just my 2p's worth