Hello Jo, I also bought the Exuma from Norwich ( Did you get it through Premier Hot Tubs for £2999) I lost my manual and am still getting to grips with stuff but i think i can help
Heating: Make sure that your mode is on 'STD (Standard) and then up the temperature till 34 degrees ( I say this amount because I also had kids party last week and 34 was idea) When you first adjust the temperature to 34 it will flash for 6 seconds and then it will display the actual temperature. Once again - make sure the mode (M on the control panel) is on STD (it will not heat on eco or slp). Aftre a few seconds the heater symbol will come on ( it is 3 verticle wavy lines on the right hand side of the control), the fountains will also be operational so switch those on using the star valves and it will start to heat up. You will see a low vibration around the footwell and the filters will be operating. It is best to put your lid on as this will heat it quicker but it does take a longgggggg time, start heating a good 4 hours before they arrive. If you operate the jets then the heating switches off but will switch back on when the jets are off
I hope this helps, i check this forum regulary so keep posting. I am also a newbie but i do have the same hottub from the same place and I am thrilled with it ... especially as it has just gone up £400!!!
Terry