I can definitely help with this one. I work as the director of the brokerage at Angel Investment Network. I've seen more pitches than I can shake a stick at.
First things first.....don't ever pay an upfront fee for pitching. We never charge our attendees anything, it just isn't worth it. There should be no reason for any of the pitching events to do so.
My main reason for saying this is because the matching process is too inexact. On any given pitch day we can fill the room with 50-80 investors but they are from a host of different backgrounds and you are nested among a host of different companies. The likelihood of an investor in your case coming from a recruitment background is relatively slim.
That said pitching is not a waste of time, there is always value to getting out there and at the end of the day you are only spending your time. You never know who you will bump into and you might just as likely pitch to a potential customer.
My concern for you would be you aren't a high profile B2C app or new FMCG brand, which tend to be the event show stoppers.
I would actually recommend rifling through Linkedin to approach investors with a relevant background. Make sure if you approach via Linkedin you keep it exceptionally brief and work on intrigue - I receive dozens of Linkedin messages a day and it's really hard to read them all. So short to the point and ask a question at the end (just focus on getting them to say 'yeah sure').
If you are hell bent on events then some of the main ones are Angels Den, LBA etc. Then there are the novelty ones like 'Pitch to Rich' which virgin are doing. Other good pitch days are the demo days at the end of some of the top incubator programmes like Tech Stars of Wayra - primarily because their audience is specifically attending for Fintech in the case of Tech Stars.
I hope some of this advice helps - please feel free to call if you would like any further input. I know the London Start-up scene pretty well.
As said above you can't 'package up' an angel. They are individuals and on that basis some will like your business and some won't. You are however best, by the sounds of your business, to go for value add investors as it sounds like your business is quite B2B.