another fiesta with a heater problem !!!!!

[poorly festa]

hi guys,
brand new to site, bit of a novice on the spanners too! but need help and guidance so here goes.
since my car got nicked, i have been driving my girlfriends 96 fiesta diesel. blew only cold air thru the winter so changed heater valve with brand new part at a cost of £40. I dropped part prior to fitting (probably due to frost bite) but it appeared to have no damage , i don't know how fragile they are ? now blows only hot air!! under advice from "bloke at scrappy" i've now replaced the centre console bit with the heater switches, and guess what??? yes I'm still driving the equivalent of a 3 door pizza oven! any advice will be greatly recieved.
cheers
poorly festa

[Pigeon]

Check that the valve is actually being operated when you move the control. Sometimes cables/rods/etc fall off unseen when you're putting it back together. I once boiled myself and 3 mates this way by fixing a heater leak the day before a long hot journey