Have you got enough complete tile to do as I suggested early on and make a section of mirror and put the rest back around it ?
you can get mirror cut to the exact size (I advise you ask for safety backing to be applied
) from a local glass supplier
or buy a mirror from B n Poo ,Wickes etc and border it with a sheet of mosaic as a feature perhaps
this is very easy to do , and relatively cheap ,I doubt any similar tile you find would even be a close match , and then it would look odd .
then ,in a few years when you have the important jobs out the way (like getting your cars sorted
) think about a remodel
also, burning new £10 notes will not generate enough heat to keep a JLR product happy ,try burning £50 notes which are paper and produce more heat , you could try £20 notes,( also paper ) but you will need more of them