If booking so far in advance I advise going with one that allows you to cancel for a little or no fee.
I thought I had a good price for August but now cancelled as I found a rate £45 less.
Just had a quick look AutoEurope look the cheapest via Quidco who give 8.5% back
http://www.quidco.com/auto-europe/?ac
small car will be £98.79 less the 8.5% = £90.39
Add a tank of gas & upto 3 additional drivers if required £126.55 less 8.5% = £115.79
Probably worth the extra £25.40 the way price of gas is going.
* Auto Europe has no cancellation fee when Auto Europe is advised 48 hours prior to the reserved rental start date.
Slightly cheaper but a little more complicated is the way I did it last month, explained in this thread
http://www.flyertalk.com/forum/othe...t/734198-holidayautos-discount-worldwide.html
This would be £121.20 less 9% Quidco = £110.30 incl tank of gas and additional drivers.
But they have cancellation fees, waived for a £5.50 fee.
7 or more days before start date £15
3-6 days before start date 50%
0-2 days before start date 75%