how bad is the nikasil issue if the log book doesnt have the liner change noted.

and:

its for my dad who has fallen in love with the grantley design body kit does anyone have experience with it and is it good quality?

 

If it at this point and time with modern fuels nikasil isn't a problem in a good running engine. The engine doesn't contain interchangeable liners they were and aluminum block with a nikasil coating. If there is no nikasil then it would be a replacement engine.
My XK8 has 110,000 miles on nikasil engine. The more common problem is the upper cam chain tensioners and the non metallic head gaskets.

 

Here's a link to the Grently site for others to view....Grantley Design Jaguar body kit styling XKR XK8Jaguar XKR 1997-2006 Conversions body kit styling by grantley design super car design side skirts

Personally, the black car on the link that has the kit molded in looks good however the cars in the comparison photos that are not molded into the body work look just like what it is, a stick on kit, boy racer style, not to my likeing!
I also hate the taillight conversion to the two round lights, again looks stuck on, if the assembly was molded in might look OK. The front clip is nice but without the complete kit it would look out of place.

Anyway my 2 cents, do what you want to your own car!

 

Take a look on ebay my car is on there now and has the body kit fitted, it is made of the same material as original panels, and is good quality.

 

dpm,got a link I looked and didn't see it.

 

Could be because it is on UK ebay. sorry not very tech so don't know how to do links.

 

Can't see a 1998 XKR on (UK) Ebay which matches the OP's description.

 

Sorry mines an XK8.

 

Sorry - brain hurts this morning. OP's car probably isn't on UK Ebay.