CGT Allowance pre and post budget

So six months into the year the CGT rates have changed. How does the allocation of the £3000 annual allowance fit into all of this? If I make, for example, a £5000 gain pre budget and another £5000 gain post budget is the £3000 allowance split evenly between the two (given the budget is 6 months in), will it all come off the first £5000 or will we be able to choose how to allocate it?

Hi,
Guidance on the change to the capital gains tax rates has still to be written.  
A calculator will be provided to calculate the gains pre 30 October and post 30 october in due course, which will determine how the
annual exempt allowance will be applied.
Thank you.