If you have no insulation or just the bare minimum in your loft it is false economy not to get it done, as your fuel bills will suffer. The more you allow that expensive warm air to escape through your roof the more it will obviously cost in trying to keep your home warm.
There are plenty of deals on insulation around for the DIY minded at present, however not everyone wants to get on their hands and knees in a not very nice environment handling not the most pleasant material. However if you can put up with doing it yourself you will obviously save some money over a professional doing it for you. We have prices for supplying and laying it for you which can be found on our price list page. The recommended thickness has periodically changed over the last few years, driven by the insulation manufacturers it is currently recommended at 270mm great for insulating your loft but not so good if you want a floor laid, more of that later.