Just make sure the company are reputable and do the job properly .....so many cowboys in this business ....look at www.pavingexpert.com to see the procedures that should be done to prevent sinking,weeds growing , etc, don't go for the cheapest company and look for refs from previous clients and drive around and ask the people were they happy with the work ....it will save you alot of heartache in the future.
they took up all old tarmac and put down more chippings/ screenings. Sprayed weedkiller. Tarmac itself is about four or five inches thick at least. they put down the kerbing and top soil in lawn as well.
They did a job for mother in law before so I know the job is good. Job fully done in about six hours. We put coloured stones through tar mac as I didn't want t big expance of black. If you want I can take pics and send them to you.or you are welcome to come have a look