Have you tried using a swivel joint or swivel socket? Maybe with the applicable length extensions?
it is a bit tight but this is what I do as well. with the spark plug socket and a wrench you can get in there. only takes a quarter turn or so and then you can turn the socket with your fingers to get it the rest of the way off.You need to use a socket and ratchet to remove spark plugs. If you get a plug socket it will have a hex on the end that you can put a box end wrench on in tight places. I have always been able to get to mine with a socket, extension and an impact swivel joint.