* Jaguar XJR 4.2L V8 SC (X350) - 2003 with 139K *

Hi All,
Looking for some advice on replacing the front drivers side (UK - offside) air suspension strut and air suspension compressor.

I have had a noisy air suspension compressor for a while now and air suspension fault on dash after driving for around 5 minutes. However the ride height has been sort of okay. I was going to get the compressor replaced with a new one next month (I am aware of the repair kit but prefer a new compressor), but yesterday the front of the car was not looking right. I drove it and got 'vehicle too low' message on the dash. After getting back home I noticed an audible hissing sound coming from the drivers side (UK) front wheel. Obviously the strut is leaking air and the car drops at the front both sides after sitting for a while. The rear seems okay. Today I started the car and the compressor kicked in almost immediately (still noisy) and the front did rise up enough to turn the wheels fully but still getting the hissing noise of an air leak and drops pretty quickly after being parked up.

My questions are:

1) Do I need to replace both struts on the front or is it acceptable to just replace the one that is leaking air?

2) Any advice on where to buy a reasonably priced strut from in the UK? I've seen them on ebay very cheap but they are from China and I am very dubious about their quality and compatibility.
British Parts do them for £635 each and SNG Barratt do them for £749 each inc tax. (I would prefer to pay less, especially if I need to replace both front struts)

3) Should I replace anything else while getting this work done?

Thanks,

David.