Absolutely they did.
In 1996 the CEO of the British company I was working for met with James Hodge, the Ambassador at the time, and he received invaluable advice on entering the Thai market.
In late 2000 I met with the British Ambassador, Barney Smith, to get his advice on an issue we were having with the growing the same major UK company in Thailand. He gave valuable insights on the issues and the possible solutions.
Old school Ambassadors who knew what was really going on and who provided excellent support to British businesses.
Then a few years later, I met with the new Ambassador, who very smart and spoke excellent Thai, but had no real insights about the goings on in Thai politics or business as he was a career civil servant who had been sent to Thailand to sell half of the embassy grounds to Central.
After that, the Red Shirts occupied Central Bangkok - their barriers were placed on Sukhumvit Road just after the Wireless Road junction, and the whole embassy team ran back to the UK leaving us expats and our families to fend for ourselves.
After this, the embassy outsourced visa services to VFS and passport renewal was no longer possible in Thailand, so I had no use for the embassy any more.
Add in the sale of the remaining half of the embassy grounds to Central, a Bengali British Ambassador and the quick demolition of the Residence Building to ensure a preservation order, which would delay the sale, could not be applied - and we can see that the service and reputation of the British Embassy in Thailand is not what it used to be.