Disco 1 300Tdi leaky injector to head seal

A while back I had the injectors rebuilt on my EDC 300 Tdi. I used new injector sealing copper washer (Britparts) but ever since reinstalling the injectors they have all started leaking. I've replaced the copper seals a couple times but eventually there appears diesel where the injector goes into the head.

Is there a trick to installing these washers, does the raised side go up? Is there a sealant that should be used (I wouldn't think so), or do I need to buy genuine LR items?

Ridge faces up toward the injector and have you cleaned the seats in the head and checked the run off pipes and hoses could be coming from there.

What @mr glee said, also check your spill pipes, the cloth covered pipes running between injector tops. They are prone to hardening and cracking, giving the impression of a diesel leak.

The return hoses and connections are okay.

I have not cleaned the seats in the head. Any suggestions for cleaning these other than a cloth and a screwdriver?

Don't use a screwdriver you may scratch the seat use a wooden dowel/garden cane and cloth

Compressed air and a few drops of thinners should be all you need to clean any carbon from the seats, fine nylon bristle brush (much like the ones from sets you would have used on old carbs) are okay in a pinch. The domed part of the washer faces the injector as mr glee said

Well, no luck. I cleaned the seats and reinstalled the injectors with new washers (ridge up) and still they are leaking. This is becoming very frustrating.

No luck. I cleaned the seats and reinstalled the injectors with new washers (ridge pointing up) and still they leak.