Recipe: almost syn free spicy bbq sauce

I found the base recipe on the Slimming World site.  I rebelled against using the 3 tbsp sweetener it demanded (six if you double it as I did because the passata was a 500g pack) and it had a certain blandness that sent me to the cupboard and fridge for extra ingredients.  The result is really rather tasty although a good dollop of honey and/or brown sugar would have been better. 
Can't have it all, can we?

Also I gave both stages need a lot longer than it says but maybe that's just me.

Here's the original; recipe:  https://group.slimmingworld.co.uk/recipes/barbecue-sauce.aspx#recipe-video 

On the turkey burgers with a salad and some light salad cream.  Total 3 1/2 syns (a bit of flour for the burgers and the salad cream

Ingredients to make quite a lot.
spray oil (I use rapeseed)
2 onions, very finely chopped
1 tsp mild chilli powder (or to taste)
a good squidge of garlic puree
500g passata
1 tbsp sweetener (I use stevia)
4 tbsp balsamic vinegar
1 tbsp Worcestershire sauce (or to taste)
1 tsp mustard powder
1 tbsp ketchup
1 tbsp lemon juice
1 tbsp tomato puree
1 tsp Marigold stock powder
salt and pepper to taste

(It looks a long list but it's all cupboard ingredients)

Method
Put the chopped onions into a pan and spray well with Light cooking oil.  Mix.  Heat, cover and allow to simmer, then steam for ages until the onions are well soft.  Add the garlic and the chilli powder, turn the heat up and fry for a few minutes, stirring so it doesn't stick.

Then add all the other ingredients, mix well, bring to a boil and allow to simmer gently, uncovered, until it's reduced a bit and feel a bit 'gloopy' - how thick to make it is up to you really.  Taste now and again and adjust as required.

You could have it like that with the onion still in bits but I cooled it and zizzed it with my stick blender.  It was really nice.

SW info:
Apart from the ketchup, the ingredients for the sauce are all 'free'.  The ketchup is one syn but seeing as it makes ten portions of around 100mls, quite enough for me, I am going to ignore that.
I expect it will freeze well, I see no reason why it shouldn't.