Exactly.
I think, unless it is a particularly unusual property, then the EA valuation tends to be pretty close to the surveyor's valuation, as this is what both of them do all day long, for their job, in that area. Once you bid considerably over the asking price, it is very likely you are going to have the valuation come back nearer to the EA's valuation than yours, so you need to only offer what you are willing to pay.
My dc bought within the last year, as have several of his friends, cousins, etc. All at the opposite end of the market from you (ftb, and for a fraction of the money you are talking). Talking to the EAs, it is happening over and over again - there was a bidding was on each house, people got carried away, then the sale breaks down because the mortgage valuation almost always comes in around the original asking price. This, in fact is how my dc got their house - they were outbid and then the "winners" couldn't get the mortgage so the EA came back to dc and another couple who were the next two highest bidders.
It seems you aren't in this position though OP - you have the money, but were hoping for a better ltv. What you have to decide is if you can afford it at what you have offered. As a pp said, if you are buying it to live there for many years to come, then a stagnation of (or even collapse of) the market in the next couple of years is irrelevant - it only matters when you eventually come to sell, many years down the line.