Sweet spicy slow roast pork ribs

We have quite a lot of pork ribs in the freezer and hadn't got round to eating any of them - despite us both finding them tres yummy. Finally I remembered they were there and got round to cooking some.

Enough ribs for 2 people (we had 8 each - but I think they are only half length)
1 tsp paprika
1 tsp chilli powder
1 tsp cumin
1 tsp oregano
1/2 tsp black pepper and 1/2 tsp white pepper
1/4 cup dark brown sugar

Mix all the ingredients together in a bowl
Put the ribs on foil in a baking tray and cover both sides of the ribs with the rub

Put the tray in to the oven at 120°C for 2 hours
Put 8 tbl spns of water over the ribs and cover with more foil
Return to the oven and cook for a further 2 hours.
Check occasionally and add a bit more water if the ribs are getting a bit dry. You want there to be a syrupy sauce under the ribs when they are cooked, not too watery
Serve with chips and salad (the salad makes it healthy!)