Notes

I have read over your proposal and I have some notes.
I like the idea of shares in the 10gm rock, it gives people a chance to own a stake of moon rock that they would otherwise be unable to obtain.
£20 seems a fair value, do you have an idea on roughly how much that share will be worth upon sale? Just so I can have estimates.
10,000 shares at £19 each within 2 months should be achievable, depending upon your current sources and avenues. I would personally extend that target towards the start of 2020, as Christmas and New Years are VERY efficient in generating sales and last minute purchases.

The only issue I think we would personally have, is brand recognition, as I and I am sure many other 'mainstream' people who are not necessarily up to date on space agencies etc have not heard of you guys yet.
For example, I would see 10,000 shares of moon rock instantly sell out if hosted by NASA, but if people do not know of your company / brand, that is the social bridge and gap we must merge.
This is where social media shines thankfully, given some time that would not be an issue. Personally I think we are in need of a publicity stunt or some viral media creations to get off the ground.
Something that will put your name infront of as many eyes as possible, so they are ready for your announcements and to spend that money.
That's my thoughts in regards to going about the sale and your brand recognition, which is where all sales will hinge initially.

As for my part of the process, I am more than happy to have an advisory and hands on approach to helping you guys get seen on social media etc, but the current offer while seemingly generous is also a little ambigious.

For instance, while the sound of a minimum estimated value of $1m seems great, the exclusivity of the item will lightly have gone down due to the mission so I see it dropping a little. Plus it will only be obtained on a minimal sale basis in a timed manner, which with my experience doesn't always work out in this area.

For example let's say I net 4999 sales instead of 5000, that is a legal disparity which would make my work essentially free.
I am never one to work on commission or affiliate only basis, as I feel my time and expertise should not be measured by the success of a campaign where the aim and possible external issues would hinder or even break down all the work I have done.
While it's a long shot, the campaign could be shut down, there could be issues that arise that would cause sales or even the mission itself to be on hold. Which once again means all my work would have been for free, it's a large risk on my end.

I typically have a signing fee which hires me for a set period or campaign, then the affiliate / commission is on top to be a sweetener.
So I would like for us to have a similar contractual relationship as the industry standard here.
What I'd propose is a signing 'fee' of .1gm of moon rock that is the standard base cost, with a milestone 'fee' of .08gm of moon rock per 1000 sales (.5gm total at 5000 sales which includes the original base cost).
I am happy at the 5% sales as a sweetener fee, that seems fair.

Hope you understand where I am coming from, I want you guys to be a success and I think with my help, it most definitely would be.
Just want it to be fair on both sides, as I will be devoting time, giving my advice in any capacity I can, as well as using my connections, for the main payday that is 5 years away.

Let me know your thoughts.