The "Horstmann DRT2 Room Thermostat" does both time and temperature and instead of switching on and off it switches to a different temperature so you can set to 10 degs overnight and 20 degs in morning then drop to 18 degs for main part of day and back to 20 deg in evening for example.
If you also want hot water then you may need a timer for hot water but unless the storage tank is poorly lagged you may as well have water on 24/7.
Wiring will depend on system but the "Horstmann DRT2 Room Thermostat" has volt free change over contacts so will work with most systems.
Disadvantage is the two AAA batteries need changing once a year.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!