Would have to be the former P&O (previously Olau) Pride of Portsmouth/Le Havre, which I sailed on many times. They were 'happy' ships, as were most of P&O's sailing out of Pompey; rather careworn and ludicrously over-specced for the route, but always a pleasure to travel on. We would regularly go off on a wander and get lost in amongst the substantial lower cabin decks, exploring the forgotten corners - swimming pool and couchettes come to mind, along with the cinema on the main decks! Sadly they did little to stem the losses being made, offering too little freight capacity and too much unused passenger space, but I do miss my cheap jollies on them both!
Somebody already mentioned the brief appearance of the second Pride of Cherbourg. Rather the opposite, with little passenger space but plenty of room for freight. Perhaps if they'd gotten hold of a pair of them they might have turned around the Le Havre route? I did enjoy the Irish pub though, it was a slightly odd thing to look through the traditional stained glass and see lifeboats! The 'conservatory' on the back was a rather pleasant place to enjoy a few slow lagers too
On a smaller scale, the Gosport Ferry Co still has it's pair of "Queens", Gosport Qu. and Portsmouth Qu., which hail from the 1960's I believe. Always nice to cross on one of those, far more charm than their newer sisters. And, stretching 'ship' well beyond credibility, the Southsea - Ryde hovercraft is surely the most entertaining sea journey in the UK!?
