I have a 2002 Ford Focus ST170..... Can anyone give me any ideas as to why my types are wearing just on the inside on both tyres. Many Thanks

you need to get the tracking done if there are no other faults

Is it possible to track the rear tyres up?

yes on a focus 4 wheel tracking

Incorrect pressures - too high / too low, Carrying things in boot without adjusting pressures to name a couple of reasons

Your rear wheel camber needs adjusting.
You may also want to check the condition of your springs and all rear bushes for wear.

Start off simple and just get the rear toe checked out, if this is out then you found the prob if it's not then go onto the bushes. Don't worry about the camber as I don't think its adjustable on any focus, for def it's not adjustable on the mk2 st3 as I've adjusted my front and rear toe my self at work.

If you get your tyres done by a major garage they will put in the factory recommended settings sometimes they need tweaking slightly for extra weight (big sound system in boot?) if not as tomo said pressures. After that all the wheel values need checking

Pressures are not a factor in the wear this chap is experiencing. Under inflated tyres will wear both shoulders of a tyre and overinflated tyres will wear the centre of the tyre.

Depending on the type of wear he is experiancing on the inside edge could also be heal and toe wear this will appear in high and low tread blocks around the tyre. If this is the type of wear then Unfortuantely ur screwed and nothing will cure it, not even putting the tyres on the front as u will then just get a sound similar to a buggered wheel bearing and also vibrations though the steering wheel.

You can buy adjustable camber kits for the Focus.
A bit of camber is good for handling though.

Ha thanks guys for all the comments...I think I really need to go a garage and ask them if they do tracking for the rear tyres. I have nothing in my boot( No big bass boxes yet lol)..I have only just bought the car..If it is possible to alter the camber I think I will have sorted the problem because I really dont think it's down to tyre pressures like Foci_st3 said :-).