AHA! I have a solution!!

After trying all 144 and 176 codes (512 in all), I have found the following:

Code 144 Fn 62 will switch unit ON in VCR mode
Code 176 Fn 62 will switch unit ON in DVD mode

BUT only after a switch off! To change over between VCR and DVD, you have to wait 7 seconds for shut-down, then switch it on again using the 144 on code for VCR or the 176 ON code for DVD. Of course, if you can be certain the unit's already off, no worry.

Either code 144 Fn 63 OR 176 Fn 63 will switch it off. It makes no difference which one you use.

A PLAY command (10) from either 144 or 176 codeset will wake the unit up if it's off, BUT always into the mode it was in when it was switched off if there's no media loaded. However, if for example a tape is inserted but no disk, VHS will always be selected regardless of the 144 or 176 code. Go figure!

Hope this helps.