Love Alistair MacLean - I have all his books in tatty old 70s & 80s paperbacks, including HMS Ulysses. (I just checked to see whether I had 2 copies, but sadly not.)

You should check out Desmond Bagley, if you haven't already done so. Similar sort of thing, with High Citadel my all-time fave.

Guns of Navarone was fantastic, although (as usual) they butchered it for the film. I think this was one of the first times I'd seen a favourite book converted to film, and I was horrified. Where was the scene where Andreas (?) easily straightened the poker he'd pretended he couldn't bend when the tough guy who bent it in the first place was looking on?? That was a vital part of the character, and showed that one team didn't necessarily trust the other, and yet they never put it in the movie. (I haven't read the book for 20 years, and yet it still remains one of the most memorable bits for me.)

Puppet on a chain was brutal, and When Eight Bells Toll was another goodie as far as I recall.

If you like Maclean you should also check out Douglas Reeman, Colin Forbes, Victor Canning's thrillers (the Kingsford Mark ... wow) and Brian Callison. I grew up on all of these to the exclusion of everything else bar Agatha Christie and a bit of Asimov & Clarke, so they're all household names around here.

Every charity shop has about a half-dozen Macleans. They're almost permanent fixtures...