Is there an easy way of getting glow plugs out of a Mercedes-Benz E300D?

I have a 1994 Mercedes-Benz E300D, the last without any electronics. It's at 212,000 miles and still going quite well, but I have a problem when my local independent garage has to change a glow plug. They say, probably correctly, that they have to take off the exhaust manifold to gain access to these plugs. Do you know of any method to avoid this expensive operation?
What's worse is that the glow plug could snap when they get a spanner on it, so the head then has to come off and the plug has to be drilled out. Sorry, there are no short cuts on this job. The better chance they have of getting the glow plug out cleanly, the less chance of the job becoming really expensive
Answered by Honest John on

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