What will save me money/be the greenest/cost the least?

[Katymac]

I'm looking at
Solar Hot water (already have a back boiler & a south facing roof)
Grey water recycling
Rainwater hervesting (apart from the obligatory water butt)

I'm sorry if it's a question that is so basic - but for me as a novice I have no idea of the costs/savings involved - I think I can only afford one this year - so which should it be?

Should imagine the gry water recycling would be cheap. You can buy a diverter kit that involves you sawing your waste pipe from your bath and inserting diverter. this can go to oblig butt or to a leaky hose in the flower beds.
Don't fancy it myself as we have cast iron drain pipes which would bound to break and need replacing and then we would have to do the whloe house.

Don't I need a really big under ground tank?

And filters? and a settleing thingie?

Lowe energy bulbs are good, but shop around prices vary hugely.

Got them in every fitting that will take them - gradually changing fittings (as we decorate the house) so we can have them in all fittings

Do you turn off your TV ? Standby mode uses power.

Do the hot water as it probably takes the longest to pay itself back so you should do it first IYSWIM.

Also heating water costs loads of money - more than your water rates probably.

...which would allow you to save up for the next one.

Turn off telly/computer/printer honest

Close my curtains before dusk

Have cavity wall insulation

Have about 8 inches of roof insulation