Base of a driveway

For a general driveway taking no more weight than of a standard car (upto 3500kg), a layered, compacted stone base to the depth of 150mm should be adequate. However ground conditions, sloped ground and other factors may determine why a contractor has decided a concrete option. 9/10 times you'd lay on compacted stone & screed or other fine aggregate like Grano chippings. Many people also do not understand concrete and the various mixes for various applications, is he using a dry lean, blinding mix and laying blocks on top of the concrete to set? Or is he doing a 'wet pour' where steel reinforcement may be needed then dry screeding over the top? You have asked a very generic question which could also have a very generic answer, however not all 'trades' know what they're doing and unfortunately you foot the bill of un needed & wrong works. On the flip side this contractor may be offering a concrete sub base because he understands the conditions of ground etc which the other contractor may not have encountered before or be aware of. Personally, if it's a basic flat driveway, I'd choose stone and screed, unless you're planning on landing a plane or two. You need more information or a break down of the sub base construction method to get any real clear answer here. I hope this helps and that I've not overwhelmed you with anything.

crushed limestone (type 1 mot) as this allows water to drain.

1 is cheaper than the other so you will get wot you pay for tbh

Crushed sub base

crushed hardcore is what we would typically use to ensure best results

Type one mot is the best product for sub base.

Never ever lay block paving on concrete for a driveway, nowhere for water to drain, will just wash away the dust/sharp sand underneath and your blocks will rock and come loose always use mot type 1 for a base which will then have weed control membrane, then your screed then your block paving

Crushed limestone (mot) allows drainage concrete is more for a lot off traffic and weight