OK my son thought England was the worst civ (he's 8), so I decided to try them on a small pangaea. After some futile attempts at Sid (against Persia, Russia, Korea, Greece and Germany), I decided to try emperor level.
The start was not great - no grassland tiles, only 1 wheat on plains and a lot of flood plains (the kind that make 0 shields). I was able to keep up with the AI in expansion, and landed a couple lux, though there were no horses or iron anywhere to be found. Not much unique to playing England. Keeping up in tech was easy. Did not get much seafaring benefit since I found all except Greece without building a boat. (Greece was on their own landmass - so much for pangaea)
Kept the AI busy fighting each other and knocked out the Koreans, first to east, then Germany (only one to west). Germany sent a lot of units in the good fight against Russia until the ROP ran out and I turned on them. Actually built a longbow army since I did not have iron yet. Lucikly I got some saltpeter for muskets. Once Germany was out I gained their iron, one less land flank, and a lot of power. From there I went after Russia. Once Russia was down to no visible cities I had magnetism and built the man-o-war. With them I hunted down a Russian galley (thought it was settler in a boat) and later their last city. Of course this started the golden age. The man-o-war was awesome. It had movement of 6! I liked it so well I DOW Persia and Greece right away to sink more ships. Soon I controlled the seas and used them to patrol enemy shores. This allowed me to move almost all my land units forward and fuel the destruction of the Persian and then Greek empire. Finished up the conquest at 1100AD before my golden age ended.
Long story to say the man-o-war was a great UU in this situation - even though I was not on an archi or continents map. Frigates have marginal value to me, so this beefed up one was fun to play. I was surprised it had any value at all in this game.
I can see the power of the seafaring on an archi map. A big stack of man-o-wars could probably keep the AI off your island with just about any kind of ship. I'd definitely keep some around to try and take and enslave enemy battleships - that would be a story to tell.
Have to try demi-god next time, though I doubt my son would think England is the worst civ anymore.