The wrens were going back to Colombo for it's re-instution as a HQ after the RN had cleared the Japs out of the Indian Ocean enough to safely assume there would be no invasion of Ceylon.
Regarding ship losses, the Lancastria was far higher than 300, more like 3,000 and remains Britain's worst maritime disaster. Missing from the list is the Arandora Star which was carrying German and Italian POW/Internees to Canada. The grand old cruise liner, one of the very first of her kind; had been converted into a prison ship, painted slate grey and had barbed wire over all her decks to stop any hope of escape. She was sunk by a U Boat, I think it was Gunther Prien in June 1940 off the west of Ireland. 600 or more people died. Very nearly all the prisoner compliment were lost and there was allegedly a lot of panic. I've seen websites slating the crew and guards, but the captain and the senior engineering officer, among others, went down with the ship. It did not sink quickly - they were dignified decent men of their time. By coincidence with the Khedive Ismail's link to my father in law, I have links to the Arandora Star. My grandfather was second engineer in the prewar era of cruises round the Baltic and Med and was a good friend of the captain and chief engineer. I have many pictures of them and some ship souvenirs. They are treasured. We have a fine picture of her in our lounge. You can see the beautiful large model of the "great white whale" from the old Blue Star Line offices in the Science Museum.