Not my area, but I'd suggest you ask on DIYnot.com
If I'm allowed to post a link (I am not trying to advertise) look at
search.diynot.com/forum_search.php?all=tarmac&phrase=&any=¬=&intitle=&forum_id=0&since=any&sortbytime=0&author=&search=Search+Forum&stype=0
and post your Q after reading a few. There are a lot of cowboys about. Never use any itinerant who knocks at your door and says he has half a load of blacktop left on the truck after overestimating and would you like a cash job. Always get a real-world address, telephone number (not just a mobile) and company name. Look up the name on the net. Ask him which local houses he has recently done, and go and look at them. Verify that the quoted price includes VAT, tree roots, moving drain covers, edging and "everything else." Don't pay until it is finished and you are satisfied. Pay any deposit on your credit card for some protection. Post your completion cheque to the address he gave you, made out to the company name on the quote and invoice (state you will be doing this before placing the order, and repeat it before work starts).
From what I've seen, you will normally need it dug out to about a foot, filled with crushed stone which is levelled with a vibrating plate, whacker or roller (not by hand), then a base and a finish topping. The contractor will (should) give you a specification which will state depths, MOT standards (the standards they work to are also used for roads and car parks) and you MUST watch and measure to see that they actually deliver and perform to spec - if it says "Excavate 300mm and lay 200mm of MOT1" then measure and examine. Cutting corners is where the cowboys make their money. Drive around your area and look at similar houses who have had driveways done, knock and ask the householder who they used, were they happy, would they recommend, what did it cost. Householders are usually very willing to slag off a cowboy or praise a good firm.
I don't like tarmac myself, but the people who do recommend a paving-brick border all the way round it, laid on concrete, and white granite specks rolled onto the top layer of blacktop for appearance. If there is no edging it will squash and spread sideways. Be sure it is laid to a good fall so water will run off to a drain. Think of any plumbing, drains or electrical work you might want dug before the new drive is laid.