Tips and Guidelines for Car Hire in the UK

Always look for a reputable car rental company. Even if the costs are a bit higher, it is more acceptable than having an accident because of a sub-standard rental car.
If you are the cramming type, always avail for the "pre-paid petrol fill-up". In almost any rental company, you are expected to return the vehicle with a full tank. Pre-paying for it will cost you a lot less than paying the penalties for an almost empty tank or a late return.
Try to get a car that runs on Diesel instead of Petroleum. This is because UK enforces larger taxes on the latter. Plus, Diesel can give you more miles of travel.
Most rental cars in the UK run in manual transmission. Automatic Transmission vehicles are pricier.
Always bring a comprehensive road atlas and always review the routes that you will take before embarking on your trip. Getting lost in the middle of your trip could cost you a lot.
Most of the major car hire companies provide a temporary subscription to one established breakdown company (e.g. Royal Automobile Club or National Breakdown). The third-party company will assist you within an hours time in the event of a breakdown.
Aside from your driver's license and international driving permit, it is also advised that you always have your insurance and registration papers with you as a proof of your temporary ownership on the rental car.