Search this Forum, I found a German company making a puller for the injectors, may have a go at making one myself in the future if I can get a look at one, I can't believe they are that hard to remove. I have posted previously about the "drip tray" that fits under the expansion bottle and is supposed to stop water getting onto the cam belt and the injectors, I got one from Belgium and fitted it. I think the water is also responsible for making the injectors difficult to remove, that and the lack of room. I would be very slow to condemn a head with an injector that can't be removed, especially if the head is off. I don't know what interval is suggested for cam belt change buy I always err on the side of caution, make sure the water pump and tensioner and idler are changed as well.