Miles upgrades - advice

Afternoon all.
I have a 'Q' class economy fare booked LHR-SFO outward 27th July, returning SFO-LHR 31st July.
The ticket was bought from Thomas Cook (wouldn't normally, but I had several £100s of their vouchers to use up).
I would like to use miles to upgrade both legs to UC. Obviously I need to pay the difference to get the 'Q' classes to 'L's first of all.
VS say this can only be done for the outbound leg by Thomas Cook. TC screwed this up a couple of months ago and I so I missed the one 'G' seat available. Nice one TC.
Well I'm hoping availability in 'G' pops up again or alternatively they let me up with miles on the day. VS have said once I've flown the outbound leg they can upgrade the return 'Q' to an 'L', as it is then 'their' ticket rather than TCs.
So the advice I'd like from you is -
1) Should I get TC to upgrade both legs to 'L' in the hope that 'G' availability opens up nearer the time (I'm checking online every day)? My thinking being, if/when a 'G' pops up I can simply ring FC and get them to upgrade me.
2) How likely is it for more 'G' to become available? Current availability for LHR-SFO on the 27th is
J7 D7 Z5 W7 S0 K0 Y7 B7 L0 M0 Q0 X0 N0
and for the return on 31st
J7 D7 Z7 W7 S7 K7 Y7 B7 L7 M7 Q7 X7 N7
3) If I DON'T upgrade the outbound ticket to 'L' prior to travelling, would they let me do that at the airport (and then use miles to get into UC), or would it still be the case that the ticket would 'belong' to TC?
Thanks for your help!
Andy
I have a 'Q' class economy fare booked LHR-SFO outward 27th July, returning SFO-LHR 31st July.
The ticket was bought from Thomas Cook (wouldn't normally, but I had several £100s of their vouchers to use up).
I would like to use miles to upgrade both legs to UC. Obviously I need to pay the difference to get the 'Q' classes to 'L's first of all.
VS say this can only be done for the outbound leg by Thomas Cook. TC screwed this up a couple of months ago and I so I missed the one 'G' seat available. Nice one TC.
Well I'm hoping availability in 'G' pops up again or alternatively they let me up with miles on the day. VS have said once I've flown the outbound leg they can upgrade the return 'Q' to an 'L', as it is then 'their' ticket rather than TCs.
So the advice I'd like from you is -
1) Should I get TC to upgrade both legs to 'L' in the hope that 'G' availability opens up nearer the time (I'm checking online every day)? My thinking being, if/when a 'G' pops up I can simply ring FC and get them to upgrade me.
2) How likely is it for more 'G' to become available? Current availability for LHR-SFO on the 27th is
J7 D7 Z5 W7 S0 K0 Y7 B7 L0 M0 Q0 X0 N0
and for the return on 31st
J7 D7 Z7 W7 S7 K7 Y7 B7 L7 M7 Q7 X7 N7
3) If I DON'T upgrade the outbound ticket to 'L' prior to travelling, would they let me do that at the airport (and then use miles to get into UC), or would it still be the case that the ticket would 'belong' to TC?
Thanks for your help!
Andy