The 51st Highland Division was deployed to the Maginot Line It was never near the rest of the BEF and could not have been a “sacrifice”. It was a victim of bad luck and a bad location.
Here's a map of their deployment in the area.
Unfortunately, the German advance was just too quick to get these units out. By the 10th, the 51st Highlands' prospects of evacuating out of La Havre had pretty much evaporated. This left them trapped and judging by the speed of the German advance down the coast, I really don't see how anyone could say they were left as sacrificial lambs. Especially when it is considered that the Navy did make an attempt to evacuate them from St.Valéry-en-Caux, though the attempt was unsuccessful since the units had not been able to fall back to the port when the navy arrived and then was forced to pull back out to sea when they came under bombardment of the Luftwaffe.
news.bbc.co.uk/2/hi/scotland/highlands_and_islands/10294630.stm