A big problem in UK is the lack of dealers. There are 100s of main dealers for the competitors, but only a handful for MB vans. They don’t sell many new, and that means not many secondhand either. Servicing can be done anywhere of course, but buying one of the limited seems hard work. Finding a good one was tough. But they’re well regarded for taxis and executive hire, so they can clearly do the miles.
I was buying in 2016, and ended up with a 2012 plate. At the time they seemed to perform very similar the T5, but were most definately cheaper on a like for like spec basis. I ended up driving from Taunton to Glasgow to buy one. I owned it 5 years, drove approx. 12k / year and trips to Hungary, Greece, Italy, Spain etc. Biggest fault was the air con compressor. Sold it before I fixed to a fellow STWer. Some rusty bolts, but not the metalwork.
Bought a 2019 plate model after that, and it just does what I want. I have the mid length ‘long’ model, and it’s still one of the only vans I have ever seen that has a full size double bed & place for bikes inside without needing a pop-top.