The first bubble canopy XIVs showed up about the same time as the first bubble canopy XVIs, meaning roughly mid to late April 45. The XIVs had full span wings from all the photos I've ever come across. Many were clipped post war.
So yes Johnnie Johnson had a low back XIV at the very end of the war
I'd preferr the XII though
The late Terry Spencer in his high back XIV that he had while commanding 350 Squadron RAF. He was shot down by flak in this bird and made POW but managed to escape by stealing a motorcycle and racing back across the Remagan Bridge.
Terry's low back XIV that replaced the one he was shot down in. He was in the wing commanded by Johnnie Johnson at the time and would have had this bird about the same time Johnnie had the one painted like the pictures Furball posted.