Edit:
West Acton - Oxford Circus = 23mins
Oxford Circus - caledonian road = 11mins
= 34mins
add extra minutes for walking to west acton? - If your closest tube stationis park royal that is
extra minutes for changing tubes at oxford circus during rush hour
extra minutes to walk from islington to caledonian road - or to go to caledonian road from islington via tube
surely it would be quicker for you, and a lot less hassle to simply get on the tube at park royal and get off the tube at caledonian road assuming those are the two closest stations to where you are staying and where you are working