You might be able to pay money into the account before you go and increase the amount that can be taken by a hold

e.g. have a £500 limit - pay £500 onto the card and have £1000 available credit which would allow for the rental to be made

This does depend on the credit card company though - some will not allow that

I would call the card company and see whether it permits that activity - if so, top up the card to enable a hold for the whole rental