Obviously good luck with your venture, but given the international nature of the community, you need to appreciate that you will need more going for you than just coming from the UK (in this area I don't think Buy British is going to hold much water). Anyway my suggestions are:
1) Stick with the younger female age group, as you otherwise have to ask yourself who is likely to be purchasing the vids of older ladies ? Younger men (unlikely), older men (possibly, but probably a much smaller market).
2) Foot tickling may be your preference, but you do need to spread the tickling around the whole bod. By all means break it into 5 minute clips concentrating on different areas.
3) I don't know about other people (interested to hear others views on this), but I wouldn't even save a free 5 min clip (or pix) to my computer, unless it includes the lady's face (laughing).
4) Whatever you do don't skimp on the quality of either the sound or lighting.
5) If you are the Tickler, we want to see as little and hear as little of you as possible. One producer insists on laughing alongside his beautiful and ticklish model, which is why I won't buy his clips. Another one has such a large bulky frame that he dominates the screen, even when trying to be unobtrusive. Most of them, all think they have witty asides which (apart from the Tickle Central guy who really does have) merely serve to irritate. The thing is if I was trying to do what you are doing, I would want to be Tickling all the pretty girls as well, but you have to ask yourself is that your real objective or is this a business venture.
6) Solicit other producers views on model release forms, and what can potentially go wrong with a model. For my money I would deem it too risky (both from a wasted shoot point of view or a potential court appearance) to tickle someone who has not been tickled before.
Random thoughts anyway, and hope they help.