Freo
Whilst there is no information about cab locations you can always look around to find it yourself. A walk around the area will normally find a coiuple in a city area.
It will normally be a green box about 1m high and 1.3m long, You are interested in the one with a number corressponding to that quoted for your line. There are some photos of typical ones
here on Roberto's site
If you are in a big block of flats ( 200-400!) there is a chance it is hidden in the basement. If so this will be why you do not have FTTC. If this is the case you will have to lobby the landlord to approach BT giving them permission to place an FTTC cab alongside and sortout the power issue OR get enough people interested to get the landlord to approah BT and ask for FTTP this is actually a better way forward in most blocks of flats as it overcomes the power issus.
As you already have 20Mb you may findit difficult to get people interested in Fibre but people at the top of the block may get less than you.