Your instructor is being reasonable in the time frame.
If you look at
http://www.caa.co.uk/docs/33/srg_lts...8_Sept2012.pdf it states :
3.2.5
....he will be given time to complete the necessary planning and pre-flight preperation, normally 45-60 minutes depending on the circumstances.
I think the amount of time he is giving you is more than adequate.
Communication not the best but your CPL examiner may be communicating in exactly the same way and your employer is likely to communicate electronically.
Welcome to your future career.
