Sounds like you might want at least a chunk of the money up front. Otherwise, hard to say with so few details I think. Do you want and need the work or will you probably hate it?

Yeah detail light sorry, much more detail and you'll know the company :-)
Some 1st contact technical demos and POC Crypto work + installs I think a retainer is in order for the Poc and demos, suppose should we up the daily rate at bit for the installs, does that sound sensible ? I've had terrible issue with suppliers not properly qualifying the deployment environment.

I can't really say, my area's more in the sports arena! Charge what you can get away with seems a good maxim when companies have money + need you badly. As far as installs go if you have a daily rate already then cool, if it takes longer due to their error then you charge more because of that already. 

Turns out it might involve 6months secondment overseas nipped that one right in the bud, I'm not spending six months living out of a suitcase in Germany I'm married and want to stay that way ...

I wonder why they suddenly don't have someone to cover that job!

He put his notice in and was put on gardening leave immediately, but there are others in different territories so I'm left wondering why and whether I am being set up for a job offer with the supplier I don't want

I am in fact not quite clear on what's going on, I did think they wanted me to Step in until the replacement could get up to speed, but the the boss dropped the 6month thing on me and I don't know any more "shrug" bit strange.

Too big a job for a new untrusted recruit maybe?

They appear to have sacked everybody in the U.K. For being a bit useless, new engineers start on Monday but have 2months of training in front of them, I'm really really busy resolving the old lots "ahem" challenges. :-)