Planning for site works

I realised that while I wait for all the paperwork to get sorted out with the solicitors that I need to keep thinking positively and to believe that this precious 5 acre site will be ours soon.  Therefore, I have decided to use this time to start planning the construction of the nursery in a bit more detail. I have already decided on all the main structures (greenhouse, storage barn, wind turbine and giant water tank) but have only a vague idea of how to get the foundations laid and all the levels right for the irrigation to flow properly. I find that I'm in a silly chicken/egg situation where I need to get quotes from Groundwork Contractors but I dont know what I need until I have engaged someone! The questions that visit me around 4 o'clock in the morning are:

• what sort of ground surface do I need to allow trucks to bring deliveries in and out without getting stuck in the mud?
• how do I keep the greenhouse clean but minimise the amount of concrete floor area?
• if my guttering is a foot higher than the top of the water tank will this be enough drop to allow the rain water to flow down?
• if I want ebb-flow trays, how do I keep them level and allow the guttering to slope?

I think I am just going to have to write this up with lots of open questions and then select my contractor based on being prepared to guide a novice through these technicalities - assuming they are not changing me a fortune for the privilege.

All advice welcome!