Thanks all. This has been super helpful. Didn't expect so many responses within a span of hours. This is indeed a very vibrant community.
I have put together a timeline of service history (and the supposedly missing and dubious ones highlighted in red and amber respectively).
As per Mercedes DSB (and also the doc shown by the indie garage/trade seller), there has been one confirmed A service. This was over a year/14k miles after purchase in February 2018.
The indie garage (trade seller) sent me a text this eve saying that the current owner has managed to find text booking of a B service at Kwik Fit from March 2020 and will get service details from Kwik Fit tomorrow.
The indie garage (masked his name to protect his identity) has also sent me the following proof of a B service at his garage in November 2020. This service report carries a SecCode. Given that it's his garage, not sure if this is faked or genuine (any way to verify this?) He did say that he is authorised to update DSB directly so wonder why does the last service report not appear in DSB yet.
Assuming he is speaking the truth on both counts, there are hopefully two more verifiable services (highlighted in amber in the table above) subject to the seller providing verifiable evidence of those services.
What's missing then is at least two services (highlighted in red) which should have happened in the first 15-16 months of this car's life when it was with another (its first) owner. Given the extremely high mileage of 45k within its first or so year and with missing service history, not sure if this was used/abused as a taxi by its first owner. Wouldn't know as it traded hands before its 3rd anniversary and hence the bi-annual MOTs as required for taxis isn't obvious from its MOT history.
The indie garage has been mum about the first owner of the vehicle (citing data privacy rules, etc.) but if I were to progress with the purchase, I would insist on digging deeper on the missing service history details and will probably ask for more discount on what's already been offered.
Also, the indie garage has been trying hard to sell me a 1-year warranty from
Warranty Wise for a very 'attractive' price of £299 over and above the 3-month standard warranty he has been offering anyway. I read the reviews for Warrant Wise online and it looks like an organised scam. So I don't think this purchase is worth the punt basis of this superfluous warranty alone.
Any other tips? Perhaps a paid inspection by RAC/the AA? Of course, all of this is conditional to the dubious service history (in amber) details shared with me. I have little hope for the missing (red) ones. Also, what level of proof should be obtained for the missing service history to be treated as genuine if it's not recorded in DSB?
PS: I just realised that I am submitting an insanely long post. I hope I don't piss you all off.
Sorry, been desperate to get a ride for a while now hence the extra effort. As mentioned previously, this is at least £700-800 cheaper than the nearest comparable deal but don't want to be penny wise and pound foolish and hence want to weigh the risks.