I always feel a little uneasy when people write with such confidence about using points to upgrade. It’s not as easy as it sounds. As @djtech writes, you can generally only use points to upgrade on the airline whose FF programme the points are with – in your case, Velocity points can only be used to upgrade Virgin flights. And Virgin, of course, does not fly to the UK.
The other issue is that, as many have already written, upgrading really is a lottery. If you buy a ticket in Premium Economy in the hope that you’ll be able to use points to upgrade, there’s every chance that you’ll be “stuck” in Premium Economy. Sometimes there will be points-based upgrades available, and sometimes there won’t be. Never simply assume you’ll be able to upgrade; treat upgrades as a welcome surprise when you do succeed in getting them.
It’s a better strategy to redeem points straight into the cabin class you want to fly in. In your case, you should be able to accumulate enough points to directly redeem Business Class flights.
Given what you’ve written above, if I were in your situation my strategy would be something like this. There are other options, but this is the one I’d use:
Sign up for KrisFlyer (Singapore Airlines)
Keep accumulating CBA points and FlyBuys points.
Consider signing up for another credit card whose points can be transferred into either Velocity or KrisFlyer, if/when it has a large sign-up bonus.
Transfer FlyBuys points into Velocity (which is the only FF programme that FlyBuys can transfer into).
Search for Business Class award seats on both the Virgin and Singapore websites, and when you’ve found an available flight you’re happy with, transfer your credit card points accordingly. If necessary, you can “top up” your KrisFlyer balance using your Velocity points (though you’ll lose about 35% of them in the transfer process).
I hope this helps. There are other, more advanced strategies but this is the one I’d start out with.