In short NO you are not being unreasonable to refuse to go drive half away round the country etc...
It is very protientually against the law to be driving, as due to the changes in your insulin routine, you have an higher risk of hypo's or hypers which impact on your driving...
You need to stablise your basic control so you aren't suffering unexpected hypos or highs, then when it comes to driving distances you will then need to work out a plan of action to sort out best way to use the pump, as it may be that you need to set temp basal rates up or down, and then test after...
With distance driving I find that I not only have to set a lower temp basal rate while driving, but another one over-night as it seem to impact on me then as well to prevent hypo's, but it all needs to be worked out, and you can't do this when you've only just started on the pump, as tomorrow and perhaps the next day your injected background insulin will still be filtering fully out of your system, which may have impact on your control..
I would phone you company and say sorry can't do etc.. if they give grief or want you to do it later in the week, say sorry nope can't do, if pushy take a weeks sick leave.. It medical reasons so nothing they can do..
Speak with your nurse this afternoon, she will also say same as me and should if your employers are iffy, provide you with a letter either today if very lucky or send one to them ASP