According to According to "Combat Codes: A Full Explanation and Listing of British, Commonwealth and Allied Air Force Unit Codes Since 1938" by Victor Flintham, 248 Sqn were still using code WR once equipped with Mosquitoes (Jan '44 - Feb '45). The book lists LR363 as WR-X as an example. However - I have found other errors in this book, so it must not be taken as hard fact.
For additional interest, see this resource also about LR363 from the ASN crash database.
http://aviation-safety.net/wikibase/wiki.php?id=70568