We took the train from Loughborough to London for the embassy experience, and we took the underground for the rest of the journey. Because there were two of us, it wasn't that big of a deal to haul the pram up and down stairs etc, and we even had offers of help from people when it looked like we might be struggling.
However, there are a LOT of little flights of stairs around. I can't say exactly which stations we were in, but it was a lot of upping and downing. If it's not rush hour, though, and you're game for the hauling (or, for the folding up the pram and doing the transferring while holding the baby), it's do-able. (and, as others have mentioned, folding up the pram might figure in when taking a bus, as well.)
It's up to you, I guess! Having two of you to juggle things makes the whole experience a lot easier, really.