Hi guys I'm looking into buying a jaguar x type estate 2.5 petrol is there any thing I should look out for the one I'm looking at is a 2004 (54)plate model 

Hi

check every thing works, especially all the electrics, transmission if its a auto, check central locking works and remotes

if its a AWD model, take it for a test drive and take it to at least 70 mph and every thing should be smooth and quiet

check the sills and they can rust completely out and it gets missed because there covered with plastic covers

service history would be nice, will give you a good idea if its been looked after

listen to the engine if its quiet, rattly engine could be dual mass flywheel and can be expensive to change, tend to go quiet when clutch is pressed on a manual

have a look on "vehicle smart" app for cars mot history to see its not required any major issues in the past

cheers

Joe

Joe's advice seems spot on Darren, but you don't mention the mileage, nor whether you're thinking of buying from a Dealer or Private. Each will have their upsides and their downs but be more aware of the Private Seller as you will have no come back in the event of problems. 

Now I'm no mechanical expert but as with any car I would start with the Service History (with invoices if poss) and be ready to walk away if there are big gaps unaccounted for or your questions are not answered both satisfactorily and convincingly. Look for any visible signs of excessive wear or lack of TLC like untended bodywork scrapes and dings, excessively scratched alloys, worn or tatty rubber door seals, uneven gaps in body sections, filthy engine compartment ... any or all of which might lead you to think that the car hasn't been well looked after. Then of course a test drive is a must when you listen out for unwanted noises and rattles, slack steering, loose or noisy gear changes, blue/grey/black smoke (especially when accelerating), spongy foot brake ... I could go on, but I'm sure you know by now what I'm getting at.

As far as I'm aware there are no known longstanding problems that should prevent you from both buying and enjoying a well-cared-for X-type ... just be careful.

Good luck. 

I buying from a dealer the one I'm looking at is the 2.5 auto box petrol with 85000 on the clock and was serviced about 6000 miles ago and it is the all wheel drive

Above advice still holds good, especially Joe's. Also check all the steering wheel buttons work properly and remember that the tail gate window should open separate to the door as well as together, always worth checking. 

And if it's reg ...VZO on Autotrader (Bracknell) then look at the advisories on the latest MOT (06/06) that states thin brake pads, worn disc and under body corrosion 'cos there will be expense looming sooner rather than later.  If it is that car then I believe you could do better than that for the money so if it were me ... I'd walk away.

The only other one I'm looking at is a 55 plate one with 75000 on the clock but that one appears to have had oil leaks in the past the issue is the 54 plate and 55 plate are the two most local to where I live and just about in my price range 

If the 55 plate is ...JLV then it looks far more promising, but of course you're in a higher price bracket. Examine the paperwork, the oil leak was noted as an advisory in June 2016, along with worn front brake discs and corroded rear brake pipes ... but none of the above appeared on the 19/05/17 MOT which had no advisories ... and it's only done 5,000 odd miles in the last year.  You could legitimately ask if receipts are available for the last year on these items to confirm the work was done.