Buying a VW Passat, is it worth it?

Currently I have a petrol ford focus and I want a diesel as I have almost an hours drive to work.

I've been offered a VW passat 1.9 tdi with 130k miles on the clock. Service history and Cambelt recently changed. Seems in good condition. Online it says the valuation is £1700 but the guy is selling it for £1000.

With the mileagege at 130k, how long could I expect the car to last, is there anything I should look out for, what mpg could I expect, anything that can go wrong at 130k miles that could be expensive.

Any advice much apreciated.

I wouldn't.
Everything is ready to fail on a 130k VW Diesel. Turbo, injectors, clutch with DMF, fuel pump etc and they're all close to a grand to fix. The guy selling this 'bargain' likely knows what's about to go wrong on it hence the price.

If the Focus runs OK, keep it.

VW diesel TDIs will run well over 400,000 miles.
It is one of the most reliable engines made, and runs much longer than a gasoline engine.
It also gets excellent mileage, over 35 mpg.
It should have had a timing belt done at 100,000, for about $300.

Evelyn is wrong about the turbo. Any diesel truck shop can rebuilt the turbo bearing and seal for under $300. Injectors almost never go bad.
You are not likely going to find a Passat with a clutch, but they are a breeze to do, and I always dump the dual mass flywheel for a salvage standard 1 piece, if it has a dual mass one. None of these are more than $400, and none are likely or hard to do.

That being said, the Passat is more expensive to maintain than the Jetta, and the automatic is the weak link, that does cost an arm and a leg, ($2500). The automatic was weak from 1999 to 2003. The 1.9 is a little under powered in the Passat as well.

Unless you know the maintenance history, you might be better off with the Focus, since that is a known quantity. But that really is low miles for the Passat.