Mega 2560 R3 won't upload sketches

Seems to be the usual boot loader problem which Google covers extensively (but it seems for my case, not extensively enough). I’m now just trying to upload the Blink example. Error is:
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer

To cut a long story short I’m as far as using FLIP to reflash the bootloader. There seems to be slightly conflicting information as to which file to use, so here is the results from all of what one might construe to be suitable candidates; in all cases clicking ‘Read Target Device Memory’ and acknowledging for 00000 to 02FFF first:

hardware/arduino/bootloaders/skt500v2/ :
Messagebox (error) appears stating ‘Address is out of range’.

hardware/arduino/firmwares/atmegaxxu2/Arduino-COMBINED-dfu-usbserial-atmega16u2-Mega2560-Rev3.hex :
Erase & Program get green blobs, Verify gets a red blob. Bottom of the screen states ‘Verify device fail at 0x00000’.

hardware/arduino/firmwares/atmegaxxu2/MEGA-dfu_and_usbserial_combined.hex :
Appears to work, but original problem uploading sketches is present again.

hardware/arduino/firmwares/atmegaxxu2/arduino-usbserial/Arduino-usbserial-atmega16u2-Mega2560-Rev3.hex :
Same as above.

hardware/arduino/firmwares/atmegaxxu2/arduino-usbserial/Arduino-usbserial-mega.hex :
Same as above again.

Can anyone suggest any means of proceeding from here other than defenestrating it?