Thanks for all that, although I am being to think the only way I will know what my take home pay is going to be is to wait for my first pay packet!
Which isn't a wonderful plan as I really need to get a fairly accurate idea before I rent out my house in Finland so I know how much leaway I have on the rent I charge

I guess I should be happy that however it is calculated the tax will be significantly less of a burden than it is here in Finland Where my current BASE rate is 36% and my total stoppages is just under 50%