Hi Rhys,
I ride a similar route and distance each day on fixed so thought i should comment.
I commute 30 miles daily (15 either way) from NW London to London Bridge. I commute on a stock Bianchi Pista, with flat handlebars and a good front brake. I am currently running an 80" gear, but that is because it suits my riding style.
I used to commute on a Dolan Precursa Track bike, using a 69" gear, which was much quick off the line, but a nightmare on flyovers and felt far to spinney.
Im on LFGSS and its a great forum, but like any forum theres a trend and youve got to do what feels comforable for you rather then what will make others 'respect' you.
I find the fixed ride more exciting/challenging for climbing and far more controlable in traffic then a geared bike (other may not agree). It took me 1-2 days to properly get used to riding fixed, but unless im doing 100+ miles a day or am riding just hills, i wont ride anything with a freewheel.
I still dont understand people who ride brakeless, or have any respect for them!