You don't need indoor hockey sticks.
You can use your normal hockey balls to train.
You don't need boards, can use the wall(I would cover any fire alarms)
No lifting, except a shot at the goal.
Do drilling(can't push the ball through another player)
Hands a part only, No hitting/sweeping.
3 meters rather than 5 meters.
Here are a few ideas on how to buy cheaper equipment.
Indoor Timber Hockey Wall Protection Skirting | Fitness Sports (fitness-sports.co.uk)
https://www.continentalsports.co.uk/hockey-sideboards
https://www.wickes.co.uk/Incised-Timber-Fence-Post-100-x-100mm-x-2-1m/p/548024?fix&gclid=CjwKCAjwpayjBhAnEiwA-7ena_LbaJ6FnyYhkM7QEifg1rCEV2jjdmtChyfQ4k9VZleR6lcrSmzpgRoC8UEQAvD_BwE&gclsrc=aw.ds £750 for a set. Happy to talk you through this.
If you have lots of money.
https://www.grimshawsports.co.uk/products/aluminium-indoor-hockey-pitch-sideboards
https://www.fitness-sports.co.uk/hockey/indoor-hockey-posts.html
A few videos to help explain the rules.
Part 2- Drilling explained at the start