Steve,
I realise that you have (probably) already booked your flights.
However I find that it is very useful to pay to fly in one cabin and then use BA miles to upgrade to the next.
i.e pay for World Traveller Plus (get cheapest available) and use BA miles to upgrade to Club World.
I realise that Club is not in the same league as First Class but it can make your BA miles go a lot further - rather that using them all on one flight.
First Class return costs 120,000 BA miles.
Buying World Traveller Plus and then upgrading to Club will only cost 20,000 BA miles - although you obviously have to buy WTP tickets (you can however still get "cheap" or restricted fares).
So for the same amount of BA miles you could get 6 return flights in Club World. Granted you would be having to spend a lot more money but your miles would last you a lot longer.
If you were feeling flush you could also pay for Club and then use miles to upgrade to First. That would use 40,000 miles (and you would be paying a lot more), but you would still get First Class seats.
Just my opinion of course
