Hello alan,
Just to put a little more meat on the bones that Royston has given,
The nose weight must be measured with the caravan on level ground, The main wheels should be chocked, and the handbrake off.
And the tow hitch set at the same height from the ground as when it is coupled to the car.
Whilst the road surface may be level, the caravan may not be, that depends on how much the cars suspension gives when the caravan is hitched.
It is often not realised that the down force at the hitch changes depending on how high the hitch is. - its all to do with the turning moments created by the caravans centre of gravity's relative position to the main wheels.
To be legal, you must ensure that the caravan nose weight is no greater than the either the lower limit of the car or the caravan.
For safety (and legality) the gas bottle must be secured and transported in its cradle in the front locker. This has the required free ventilation both top and bottom to vent any spillage of gas.
To achieve the desired nose weight, move some of the other heavy items towards the rear of the caravan, the awning is a good start.