If you're looking for a direct replacement for the broken slider, you might be in luck. The Potterton EP2 Programmer is now the official replacement for the EP20021. It's designed to fit the existing backplate without any rewiring, provided the backplate is undamaged and in good condition.
EP2 replacement programmer for EP2002 (plumbersforums.net)
The EP2 doesn't have the additional terminals that the EP2002 had (which allowed it to function as a mini-wiring center), but the core wiring should match. So, if your EP2002 was acting as a wiring center, you might need to check if the EP2 accommodates all your existing wires.
Considerations:
Since you're controlling your central heating (CH) via a Netatmo 'smart' thermostat and manually managing hot water (HW), the EP2 might suit your needs. The CH slider permanently on and HW controlled separately aligns with your current setup.
Keep in mind that the EP2 doesn't have the extra features of the EP2002, so assess whether those additional terminals were crucial for your system.
Installation:
Replacing the programmer involves turning off the power, unscrewing the old one, and attaching the new EP2 to the existing backplate. Remember to reuse the little red 'LED' cover from your old programmer3.
If you're comfortable with basic soldering, you could also replace the tiny NiCad battery inside the EP2002 to see if that resolves any issues.
Budget-Friendly Option:
While the EP2 typically costs around £65-70, you might find a better deal on platforms like eBay3. Just ensure it's compatible with your existing setup.
Remember to turn off the power before any installation work.