For some reason when on the motorway in 5th when i change down to 4th to get some speed to over take the car stutters but eventually gets there. It dosnt do it at lower speeds just on motorway. Odd thing is its intermitant so dosnt always do it?

I was thinking could this be a sign that the fuel pump is having difficulty giving a boost in presure when its already running fast for motorway speeds?

 

Might be.
You checked the fault codes to see if any are stored?

 

I dont have any kit to check faults unfortunitly.

 

You don't ned a kit, simply connect the two black connectors under the steering column and watch the CHECK ENGINE light. (CEL).
The CEL will give long, or short, flashes. A long flash is ten, a short is one, so two long, four short = 24.

 

Could be early signs that the maf is on its way out also mate but usually would do it in most gears but could be early stages.

 

UPDATE:

Had diagnostics done on the car at Subaru 4 You which picked up weak MAF so have changed MAF and air filter yet i still get occational hesitation when i floor it from a slower speed this time in 3rd? Could it be it needs new HT leads since it had new plug only a 2K miles ago?