Hello Wayne
From the numbers you have quoted I can only find four likely candidates which are Lancaster B1s in the W series.
W4192 61 Sqdn Code QR-E crashed on a mission to bomb Krupps, in Germany.
W4164 207 Sqdn /9 Sqdn / 1661 Heavy Conversion Unit. Became maintenance airframe 4443M
W4231 83 Sqdn / 1662 & 1667 Heavy Conversion Unit / 1 LFS / 1651 HCU. Became maintenance airframe 5451M
W4310 460 Sqdn RAAF, hit by flak and exploded near Kiel 4/4/43.
4212 and 4213 are Wellingtons in the W series. All RAF serials of the period had either three or four numbers after two letters or one letter respectively. Not sure what the five figure numbers are and the four figure numbers beginning 2 do not match any Lancaster serial batches.
If you have your grandad's squadron number, surname, RAF station it may help to trace the serials. Was he the pilot?
Cheers
Rob