I'm not on commission and highly recommend you deal with a specialist like Richard Grace. The car will have been put through a thorough inspection at Marios (Autoshield) and anything that Marios identified as needing to be fixed will have been fixed - hence the £4k spent on the car offered by Richard since it was for sale on the forum. Put another way, if you had bought that car privately (no warranty) you would have had an annual service bill (£1k?) plus the service would have identified and highlighted additional work required to a value of £4k to fully have the car sorted.
If you don't know much about these cars (as I didn't back in 2016 and I know only a little today) it really is better on your wallet to buy from Richard a car that has been fully sorted and has a warranty (6 months as standard and extendable to 12 months or more). You might pay more than other ads but the car will have been inspected and sorted - that means peace of mind. You might buy a cheaper car from ads, but wait for the first service under your ownership and see what the vehicle health check identifies. It is very easy to rack up a bill of £3k - £5k on these cars.
I bought my GS back in Oct 2016 from Richard and have been very pleased with my decision.
Rest is up to you....