Yes.
Appoinment after online payment is usual.
John,
Take a look at this UKBA webpage called Applying for a UK visa in the Philippines
You'll see that it's stated :-
So you can see the sequence.complete your application form, pay your visa application fee and booked your appointment all online before you attend one of our visa application centres...
If needed you can very easily re-schedule the appointment etc
Take a look here at the UKBA webpage called Booking an appointment in the Philippines
Follow the link to here - Book an appointment
John if you have any concerns or worries please do phone VFS. Many members who have done so say they are very helpful.
Here's the VFS webpage for contact details - Enquiries – VFS call centre
Here's the VFS webpage for Additional Services (optional)
This is where you'll find details of the VFS Application Centre VIP premium lounge service
Hope this helps.
Hopefully other members will be able to post their comments soon to give you the best range of experience