Well the bill isn't GBP39bn anymore as the UK is currently still paying the EU for its membership.... Thus in essence, the UK is already paying part of the divorce bill as we speak.(…) the bill was set as of end of March 2019 and the amount the UK has paid over the previous 3 months (which will become 7 months) can be subtracted as far as it concerns its contribution to the EU budget.Then again we've a whole number of new MEPs from the UK which may receive an EU pension (unless those of the Brexit Party refuse money from the EU, which I doubt they'll do).
The UK is currently paying for its prolonged EU membership indeed, but whereas it hasn't made it into the British press yet because they are too pre-occupied with reporting on the leadership contest in the Tory Party, there's going to be a nasty surprise at the end of it.
One should remember that the 'Brexit bill' consists of 2 parts:
1 - a small sum for the transition period in which the UK would be out of the EU, but still making full use of all the prerogatives of EU membership:
2- a big sum for future liabilities taken on during the UK's membership of the EU, based on the UK's size and membership's length.
Since the UK has effectively extended its membership, the calculation will have to be redone, taking into account many new liabilities which were taken on meanwhile (you've mentioned a bunch of new MEPs as a nice illustration, but there's much more in fact, albeit too technical to explain here now), so this part of the bill will definitely go up significantly.
Also, since the UK isn't any more ready than it was at the end of March, it's in just as much need of a transition period still than it was back then: the cost for that period during which it can continue to make use of its prerogatives simply carries over to the new transition period, whenever it starts... and may go up as well, since costs escalate over time and the running costs of the EU in say 2021, won't be the same as they were estimated to be for 2019 of course.
In short: the exit bill is getting bigger and bigger as time goes by.
TM's government did its very best to present the bill as probably somewhere towards the high end of the thirty billion range, but estimations from Brussels have consistently put it at around 45BN... and problably close to 50BN even, by now.
Such a huge amount of tax payer's money should only be handed over by the British treasury after an explicit direct approval of the British people, IMHO.