Someville ground, G-ABCD request departure information and taxi instructions for VFR flight to elsewheretown.
Bit long-winded. Where I fly (full ATC) booking out is required in advance, so they already know where you're going. The radio call needed is no more than:
Someville tower, G-ABCD taxi.
They will then tell you runway and QFE/QNH and give taxi clearance and instructions.
As part of my flying training I have 'requested an FIS' a few times. What is quite interesting from what you post is that there seems to be no real need to request it explicitally because if you establish two-way then you get it anyway.
No. You can establish two-way communication for other purposes. In particular you can call London Information for all sorts of things, such as requesting the status of a danger area, without either asking for or receiving flight information service. You can call London Centre for a practice PAN without establishing FIS. You can call
any station for a radio check without establishing FIS. You can call the tower for permission to taxi from the parking area to the fuel pumps ... and so on and so on.