I have been told that my mri has shown disc dehydration and hip inflamation, i get a lot of sciatica, is this linked?

Which Disc number?: It depends which disc is dehydrated? The inflammation of the hip where the sciatica runs could also be another cause of the sciatica. Usually the lower lumbar disc are the ones that cause sciatica. Try and find out which disc it is and if there appears to be any compression on the nerve.

MRI: Could be related. Seek guidance from a spine surgeon who can direct a steroid spine injection at the appropriate level. See what symptoms improve following an injection. If symptoms linger, the hip may be the culprit. You also may have arthritis in both places hip and spine causing pain.

Sciatica: Pain in the distribution as you suggested describes the pattern of the nerve that travels in the leg called the sciatic nerve. The sciatic nerve is not the cause of the pain source, it is the result of an irritated nerve typically in the lumbar spine (low back) which are caused by herniated disks, spinal stenosis or degenerative disc disease requiring further evaluation by a spine specialist.