Question about receiving the visa

I am being sponsored by my long term partner outland at the London UK visa office. He is a permanent resident of Canada.
My question is this. When (If!) I am asked for my passport, if I take it directly to the visa office myself, will the visa be issued immediately, i.e. same day? I know that if its sent by post it can take about 2 weeks or more before I get it back.
Also, if I get asked for an interview but get approved after the interview, will my visa be issued right away?
Its such a stressful time as everyone going through this knows, all the waiting and not knowing. I just want the process to be as fast as possible!

Thanks in advance!

Also, if an interview is requested, how long between the interview request and the interview date?