Start by separating appearance from condition
If paving is sound but covered in dirt, algae or moss, cleaning may be the right starting point. Dark spots can need targeted treatment and may not disappear completely. A cleaner appearance does not establish that a patio is structurally sound, so look for movement and damaged slabs as separate concerns.
When jointing changes the job
Crumbling, cracked or absent mortar can make a restoration discussion worthwhile. Preparing failed joints and repointing suitable paving is more than a wash. Jointing should not be used to disguise movement: a rocking slab or failed base needs its own attention.
Think about the final finish
Sealing and colour enhancement are optional for suitable paving. They need proper preparation and conditions, and can change the appearance. An existing sealer should be identified where possible. Do not assume that another coat will hide deterioration or remove the need for future care.
Build a useful enquiry
Photograph the whole patio, the joints and any problem slabs. Give approximate dimensions and mention access, drainage and past treatments. Ask for cleaning, preparation, jointing and optional finishing to be distinguished in the quote, including any return visit or access restriction.
Make the decision around the actual surface
Choose cleaning for removable contamination, consider restoration for appropriate joint and finish work, and address structural problems separately. There is no universal price comparison with replacement because condition and scope vary. Talk through the limitations before deciding.