Might I recommend 'Gallipoli' be Alan Moorehead, originally published in 1956 but available in more recent editions.

I take your points about Eric's song - one of the best ever written. But they didn't give him a tin hat (they weren't available in 1915). And he didn't land at Suvla Bay (it was 1 Irish Division and 2 English Divisions), and the Turks weren't ready. I imagine he was really describing the landing at what became known as Anzac Cove, as you say a mile north of where they should have been. Even there the Turks weren't really ready (they were covering the beach at Gaba Tepe where the troops should have landed. But the terrain was truly terrible and the Turks reacted quickly enough to hold them there. It was here that Mustapha Kemel arrived and organised the defence.

The Gallipoli peninsula had always had many artillery fortresses. They were the key. The Turks didn't want the Russian Black Sea Fleet to have access to the Mediterranean in time of war and that was the main reason for those forts. Fixed fortifications were difficult to overcome (impossible without heavy guns).

Perhaps the confusion over the loss of the two British battleships occurred because nobody on the Allied side saw them sink. They were both mined, under heavy Turkish shellfire and abandodned by their crews. And they were never seen again. In addition, the battlecruiser Inflexible had hit a mine and was limping back to Tenedos.