I have a very small, courtyard style garden with a small lawn that,due to its aspect refuses to thrive.
Its more moss than grass (where it grows) so am thinking of having it paved/flagged over instead.
What sort of prices can i expect to have the lawn removed and flagstones laid?

Astro turf, the new push stuff is very good. Will be slightly more expensive than paving it but much nicer

I’m tempted by that, but the lawn is surrounded by trees/bushes etc that drop a lot of debris & i don’t know how well astroturf will stand up to repeated raking.

Just vacuum the astro-turf….

Real Indian stone about £20 per metre square. Cheaper, less nice concrete options are available.

Natural stone and Porcelain tiles from Riverside Garden Centre

Concrete or tar it, cheaper and less maintenance needed

Indian stone will last longer and look better than concrete. If you are doing it yourself then you need to factor in removal cost of lawn (lots of trips to the tip or a skip) and sand/cement. If the sizes don’t fit your lawn area (most are 30/60/90cm) then you may need a cutter to cut to size.
If you are paying someone obviously their labour costs.

Artificial lawn is much better than it used to be and easy to brush of debris. Most don’t need sanding like the old ones did. Prices again are around £20 sqm. Much quicker to lay (remove old lawn, blind with sand, lay weed suppressing membrane and roll out lawn and secure. They tend to come in 2 or 4m widths.

OP roughly what size is the area you want doing?

You can lay a small area yourself, it’s not hard as I managed to do it! I would also look at artificial grass as that’s pretty good now (and runs from reasonable to expensive) and again something you could quite easily lay yourself.