I have 2 tomtoms one xl and go 720 both running SE navcores. The problem I have is neither will shutdown on power off! they go into hibernation I think as soon as I press the power button the map screen shows ie no tomtom drums.
please any help? thanks

If you ask for help, than we have to do the same.
Without complete info about your devices it is impossible to give any advise.

Sorry ! ok tomtom one xl 32mb bootloader 5.5259 navcore SE 9.053 map uk 870_3406 and tomtom go 720 64mb bootloader 5.5259, navcore SE 9.2.5 map western europe 870_3406

Well, your bootloaders are both not genuine for the devices, for the 720 it does not really matter, for the XL you should check the transfer rates when connected to the PC.
I use the 9.004 on my 730 and if I turn the device off it goes into sleep mode.
I assume the same happens on your devices.
Try to hold the power button for 15+ sec. to shut the device down, that will force a shutdown instead of entering sleep mode.
It might also be a problem in your memory, so do a hard reset (hold reset for 30+sec.) and run the TT clear flash tool 3 times.

That is the problem I dont want the devices to go into sleep mode everything else is fine

As I said: Hold for 15+ sec..
Otherwise you'll have to try a different Navcore.