We have a spares case that contains 90% of the tool sets that ISN'T on the shelf. The correct procedure is to scan the the replacement part and then coupon 100% off the value, this generates the replacement item to come into store for the next person.
The only time we will need to send for the part is when it is a really obscure part of the set or its a old obsolete part not carried any longer.
All items/parts are now covered under warranty to try and prevent confusion in store over what was covered. In theory if you walk in with a stripped rachet you should have it repaired with a new mech, chances are you will get a new one.
Like everything in life the nicer you are to us the more likely you are to get someone who will go above and beyond to get you want you need.
Im always nice to people............ When I wont something............ For Free. 
Below is taken from a few years back when Halfords wouldn't replace anything without a Receipt or the Wrenches from there Tool Kits. 
My large Wrench from the 150 Kit been jamming on clockwise for a while now, so decided, whilst passing my local Halfords Shop to pop it in and push my luck. No receipt with me but managed to find a orange Halfords bag in the boot, so popped the tool in the bag and in I go, goes something like this -
Me: walks in pops the bag on the counter and says "Hiya, it keeps jamming in clockwise mode"
Saturday Boy: Opens bag, takes out wrench, looks at it, "Do you have the Box for it?"
Me: "No, its from your 150 piece kit, comes with life time guarantee"
Saturday Boy: "Do you have the Kit with you"
Me: "Yes, its in the Boot, you do want me to go and get it, its just that thats faulty the rest is fine"
Saturday Boy: "No, thats fine" then starts playing with the small lever whist looking all over it again and says "Have you been using it as a Hammer?"
Me: "No, it gets used as a wrench, I use a Hammer as a Hammer, which is also in the Boot, do you want me to go and get that!"
Saturday Boy: Laughs, and then says "No, I'll go and check if we have one", walks off and ask's another Person.
Me: At this point I starting to think, now this where its all going to go wrong.
Saturday Boy: walks back "I'll have to order you one as we dont carry spares for this"
Me: "Oh, can you not give me one out of one of your Kits as I need it this weekend?"
Saturday Boy: Walks off and ask's that other person again, gets pointed elsewhere, disappears for about 3 mins then walks back with a new 150 Kit in his hand, opens it in front of me and hands me a brand new Wrench "there you go Sir"
Me: "thats Great, Thanks, and can I have my bag back please".
Love it when a plan comes together, 
And that is how it should have been. We always split sets if we need to its easy and the tools always end up being used in some way.
Don't get me wrong I'm not painting my employer as being whiter than white. Clearly they are not - before I started there part time (while I get my business of the ground) I hadn't set foot in a halfords since I passed my driving test.
The problem with them I think is that like a lot of large business ideas /process change and how it comes down the line is flawed.
Even staff have problems getting things sorted out from other shops ignoring ringing phones from an internal number is a classic. You can bet ringing the outside number from a mobile will have it answered in 2 seconds.
It narks me when you here stories from people where clearly the person serving them couldn't be arsed to do the job properly. Our old manager was of the opinion that you do what ever it takes to make it right we basically had free reign and it showed, zero complaints in a year and full bonus collected. It can happen that you find a decent halfords it's just quite rare
