Go to skyscanner.net and select car rental at the top.

I've rented from Sixt during our Scotland holiday a few months ago. They were the cheapest at Edinburgh airport (at least of the big companies). You may have to walk a bit further to their service desk than with Hertz or Avis but I don't mind that.

On the other hand, if you rent at airport you often have to pay an additional charge, so it may be worth checking prices elsewhere (e.g. in city centers). 

I have found Avis to be one of the more competitive when renting in the UK, particularly when picking up from one of the main airports. 

Also when searching try and look from the UK site rather than an overseas Avis site as the costs are always higher. 

http://www.carrentals.co.uk/

And lots of tips and search engines here for keeping costs down: http://www.moneysavingexpert.com/travel/cheap-car-hire

Pardon me but all of you who say that one company is constantly cheaper than the others clearly don't know what you are talking about. There is no such thing, just like you cannot say that one airline is cheaper than others, it all depends. Thank you.

www.europcar.com

Never had a problem and if you prebook it is so much cheaper. Plus if you do it via easyjet you get 10% off

Kayak.com is good for comparing prices.

Beware of extras on UK car rentals; even if the company website quotes you a "Fully inclusive rate" they will often sting you for CDW and insurance excess waiver when you show up, so it's worth checking what, if anything, your credit card covers.

Also beware that when they are busy some of the big players at Heathrow don't bother inspecting cars properly when preparing them, so you can end up paying for someone else's damage.  (They will often refer to small damage as "nothing to worry about" when you point it out at the start of the rental, and then add a charge for it a week after your return.)

I normally use Enterprise in The UK because they are bit more friendly and reliable than the other big names.

Andy

Thank you all! Really useful

At this moment, best rates at greenmotion via skyscanner.

Cheers Catalin!

I now use www.carrentals.co.uk. It is a fast and easy site to use and compares reputable car hire firms.  If you have time you can always phone these firms to see if they have special deals but that is time consuming with little guarantee of success.

Have compared easyjet discounts and find that they are not such good value.

Have used www.easycar.co.uk in the past with no problem but then had problems accessing the website and found carrrentals

I know of no car hire company that offers complete CDW in its offers.

Also beware cheap car hire companies - sometimes it is not possible to obtain a zero CDW even at an extra price (Patrick Locations in Geneva is an example

hostelworld.com has just started a search function to rent cars from the big names at a good price.

if you have any bank/credit card thats uk and a uk address you can use the online renting is a fair bit cheaper to use UK than a Swiss address.  I have one for 3 days in september an I am saving about 30 francs, obviously for a week or 2 that will add up to a big difference.

Hi Rachel,

I expect you already planned your trip and vehicle hire.  Let me know if you need any help and whether you booked with Sixt.

Gary - Sixt Customer Service Team 

I rent a car about every two or three weeks in the UK.

I use moneysupermarket.com, but check the price on Europcar too.

Beware Green Motion. I f you are going from Gatwick for exam ple you have to leave the airport and take a bus to a loccal hotel to pick up your car, and reverse the process when you drop it off.This adds at least 45 minutes each way.

The only other thing you might worry about is excess insurance. This is provided by the rental agencies themselves and brings the excess down to zero and covers the damage to windscreen and tyres. It usually cost s about 10 pounds a day.

However you can buy online an annual excess policy, which has the same function. These are around 60 pounds a year, and include key loss too( a 200 pound charge otherwise). I think I got mine through the AA website.

Actually Europcar issue a promise that if you can find the same rental cheaper they will refund double the difference.

Which is quite funny because you can often find the same rental a lot cheaper.

Infact on my last trip to the UK i hired a car for 12 days from Europcar and they ended up paying me to fire their car.....and I gort an upgrade too :-)

Thanks Bruce

Too late..! Green Motion came out best.. and I was/am aware I have to take a shuttle to the hotel (which I don't mind).

Off tomorrow, so thanks again!

:-)