Don't be too disheartened bud. It's reasonably short notice plus there was a ride out to wales last weekend (although I personally went in the opposite direction to participate in the mag euro day of action). Sooo a bit of a clash there. It happens.
As for giving the full charity details.... yes it would help. however, the fact that your start point etc is combined with your works charity event is good enough for me. I can't offer to come down and ride with you. Its armed forces day on the 30th so as an RBLR member I'll be busy with that. However if I can find a window I'll get up the ponder to say hello.
Total respect for what your trying to do, I think it's a fantastic idea