@Mumtofourandnomore
All the below makes quite a lot of assumptions but ...
If you have a 25kw boiler (typical) then :
3 hours a day heating @25kw for 120 days a year = 3x25x120 = 9000 Kwh
2 hours a day hot water @25kw for 365 days a year = 2x25x365 = 18250 Kwh
For a grand total of 9000+18250=27250 Kwh.
So from this the good news is it seems like your gas bill is about right (you may have a different power boiler, plus a number of other factors that affect the final result).
The bad news is that there probably isn't much doing apart from cutting back.
Your hot water/shower bill looks a bit high compared to mine.
For me in my house 1 hour a week @ 25kw heating gets me 6x showers. So for me each shower is approx. (1x25)/6= 4.1 kwh.
If all your hot water is used for showers (good approximation) and each of (6) you has 1x shower per day, then :
2 hours per day @ 25kw gets you 6x showers. So for you each shower is approx. (2x25)/6= 8.33 kwh.
So your cost per shower seems about double mine - a bit high for reasons unknown. If you can get your cost per shower down to the same as mine (4.1Kwh) then you would effectively halve your hot water bill for gas to around 9000Kwh, saving 9000Kwh of gas. This would save you 9000x0.07p=£630 per year at the lower tariff (0.07p per Kwh) and £1350 per year at the higher one (0.15p per Kwh).
Of course now you are probably going to tell me you all have baths.
There is little you can do if you have a combi boiler, apart from maybe turning the water temp down and limiting the shower time. If you have a system boiler (big hot water tank/cylinder), there are maybe some opportunites for optimisation. I managed to cut my hot water gas bill by 1/3 by trimming the amount of time it is on for. But you need a good thermostat - I have Hive which has 15min resolution and is daily programmable.