Probably, a clicking sound is a better description of the sound when I try to start it.

I am assuming the battery is flat, although there have been no signs of this being the case.

I am now charging it.

It's a Land rover battery, so could well be the original one (2006 TD4).
If after charging all is ok, then I will look to get a new one.

Definitely the battery. I tried the battery from the wife's car and it started first time.

I have never known a battery get so low without obvious signs.

Good work on fitting the window motor [emoji1]