50m2 is quite a big area – 6tonnes.
I would guess a couple of days total – to remove existing, touch up and level with sub base and lay 6tonnes.
I’d guess £750 materials, 3 man gang, 2 days inc mini excavator, roller and hand laid, another £1,250 to £1,500.
So £2,000 to £2,250 would be my guess, unless you are in London or somewhere more expensive.