Hello Jonny,
Yes, I have that Hazet tool also. It is great for getting at any individual IP line fitting. I also use a special MB crowsfoot tool which came in the original factory tool kit of a 300SL. It works well also. If I am going for a complete removal, often times I just use a standard 17mm open end wrench. Work from back toward the front. As each fitting is unfastened slide the 17mm fitting up the line and out of the way, and move to the next one. Quite simple and faster than messing around with any awkward crows foot.
For the 19mm injection pump fittings, I use a standard 19mm deep six point socket (1/2 inch drive). You may have to search around for a good quality socket with thin wall and deep enough.
Yes, standard "line wrenches" are a must for brake lines, hoses other fittings etc., but no use on the IP since there is no room to use them.