Location, location, location
Anything starting with a 6 is good. I did my FI course in 2003 and it cost me almost that then including HOTAC!
Like all aviation courses look at cost of accommodation and how many aircraft they have in the fleet available to your course as well. If you go to a school with 2 a/c and share that with other courses PPLs/CPLs etc then one a/c goes tech you find a weeks delay may cost you dear in accom etc.
From the flying perspective as well look at the surrounding area for airspace/environment. If you do your FI course from a small grass airfield vs a regional or even large commercial/international airport the differences in your time aloft spent transiting will be different however so will you experience of trying to instruct in this sort of enviroment.
So choose where to train keeping in mind where you want to use your qualification afterwards.
Final top tips do not wait to loose the night restriction do it with your initial course straight away and bear in mind that some schools will only employ instructors they have trained so if you are limited nearby your choices may also be similarly constrained.