If you have a stash of American Airlines AAdvantage miles, this Hertz promotion may be of interest.
Valid until 30th November, it offers 4 AA miles per US$1 or equivalent spent on Hertz rentals in the U.S., Puerto Rico, Mexico, Canada, Belgium, the Czech Republic, France, Germany, Italy, Luxembourg, the Netherlands, Slovakia, Spain, Switzerland and the United Kingdom.
The snag is that you must use the AA corporate code for your booking (see T&C’s of the promotion) which may not be cheaper than any other rates you can access – although it is worth trying it.
If you don’t collect AA miles, note that Hertz is not a British Airways Executive Club partner. However, as I explained in this post you can earn 300+ Avios per day when renting from Hertz and crediting it to Iberia Plus. You can then transfer your Avios points across to BA or avios.com. (Note that references in the linked post to BMI and Europcar should be ignored, as that partnership has now ended.)