When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If the car is around, you can check by yourself. The battery is on the right side in the trunk. You have to pull the trunk bottom panel, then the side panel over the battery (they just pull off, no tools). You should then have access to the battery. It is held by a brace, as pretty much all batteries are. It's 2 nuts on 2 rods. As the battery is in the trunk, possible hydrogen needs to be handled, so there should be a vent tube on either (or both) ends of the battery. Should be a small diameter tube fit to the lid of the battery, nothing too complicated, and need to be fitted to the new battery the same as on the old one. FWIW, now might be a good time to upgrade to a maintenance free AGM battery.
Of course, if you replace the battery, you will need to reset the windows (search window reset) and might be prompted by the radio code.
Kwik Fit are exaggerating the time and complexity of the work involved unless their labour rate is £200 per hour. This is my 2005 XK8 but the battery location is the same on the 1998. If you go for an alternative battery make sure it is a vented type. The vent tube goes from the left side of the battery and out through the luggage compartment floor.
When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some information about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.
when you install a new battery not only must the vent tube be connected on the side with the positive terminal; the battery's other vent on the negative side must be plugged. many batteries have two vent ports and these cars only have one vent tube. the battery should have a kit with the necessary fittings taped to the side. AGM's also often require the vent connection as did mine.