wont start facing uphill

Got a 2005 defender TD5 67000 miles owned for 5 years, been fine spot on couple of months ago fuel pump started making a load of noise had this replaced, since then failed to start any time and temperatures on first key turn always started first turn before. So then had new fuel filter housing still got same problem. Then had injector harness and rocker gasket. Since then if left on a hill for more than 5 mins wont start takes a good 20 turns to start like it is full of air. When it does go it drives a few yards then judders to a stop and then takes a lot to start again but when running spot on and loads of power no bother never misses a beat no miss fire. Then had new one way value to stop diesel going back still no difference anyone got any ideas. New pump working fine and fuel regulator not leaking.
Had injector copper washers done last week and still the same any ideas anyone?

When I had a similar problem on my (petrol) RR, it turned out to be a minute leak in the fuel line. I'm not familiar with the TD5 engine, but I would say you need to park it uphill, and then, after a suitable period, see whether you are getting fuel at the injectors.

Another possibility (and this would be a real pain to diagnose) is a bad connection on a sensor or something, that gets worse when parked uphill.

Next time you park uphill and are 100% sure it will actually fail to start (before trying to start it) go through the fuel bleed sequence (ignition on and 5 presses of the accelerator - check your manual?) then see if it starts first turn. If it does then there is a high probability you have air in the system and/or the fuel is draining back to the tank, that way you eliminate most other possibilities. You said it only started after the pump was changed so I'd be looking at the connections there for a start and then at the pump itself, don't know if they are fitted with non return valves but just because it is new doesn't mean that it is working properly (especially if it is a cheap aftermarket pump)

Used to come across this a lot with Vectras, specifically DTI16v ones. They had to be parked facing down hill, usually removing fuel filter and liberally lubricating the seals on there would cure it. Otherwise they went off to auction. However as you have had pump changed I would concentrate on making sure that is all tightly done up.