I recommend you instead find your local Kodak store and give them a visit. They will be much more clued up and might even be able to do your prints and CD while you wait. In the past I've found them to be very helpful and good.

Or go to a branch of Jessops as they are pretty good too.

Trying to get a supermarket photolab to do anything out of the ordinary is a tall order as Alex said.

They probably got confused with the slide film as their automatic film scanner is probably expecting negatives so if they scan you slide film through it the software were end up inverting the colours, producing a negative picture. That is easy to fix at home yourself but a store such as Kodak should be able to do what you wish without such hassles.