This thread looks pretty straightforward, but I've made mistakes with Moto phones before (flashed wrong SBF to a Defy a few years ago), and have generally stuck with HTC.
Background: I purchased a phone off eBay that seems to have had wrong firmware/recovery/boot.img flashed (splash screen is different to my wife's phone), so at the moment nothing works apart from fastboot.
Does it matter if I don't flash the same android version as was previously installed (that's where I screwed up with the SBF)?
I've matched the CID and model type (2GB ram) and downloaded the 6.0.1 firmware image (XT1541_OSPREY_RETEU_2GB_6.0.1_MPI24.107-55_cid7_subsidy-DEFAULT_CFC). I'm assuming that as everything is being wiped and re-flashed from scratch with a factory image, the previous firmware is irrelevant.
Thanks to anyone that can confirm.
It is best to flash the same version, or go newer... it is highly recommended, and not supported, to do down in versions. I am not sure why flashing the same version on your old HTC would cause a problem, I have had many HTC devices in the past and in a stock locked/S-ON device flashing the same as was installed version was never an issue.
Due to the state of the phone I would flash the latest XT1541 EU version, remembering to follow every step including factory resetting. If you can't access recovery, I would use the fastboot commands "fastboot erase cache" and "fastboot erase userdata" before starting the process...
Remember that some of the erase commands take some time, in some cases 10 minutes or more... Also remember that he first boot takes an excruciating long time, sometimes over 15 minutes where it appears to be doing nothing at all, just be patient (OK, maybe it's not really 15 minutes, but it seems like forever).