15+ year old Glo Worm back boiler repair or replace with a new Combi.

[AndrewHarris]

So I've got a Glow Worm back boiler fronted by a gas fire, at least 15 years old probably a lot more.
The water heating makes a row as there is a partial blockage in one of the pipes - this I believe to be resolvable with a power flush and pump replacement.
The front fire is spilling fumes and has been disabled as unsafe - this may or may not be resolvable, but we would like a working fire in the living room.
I could spend £700-£800 to effect repairs but with no guarantee that I will have a working gas fire at the end and as the fire is fitted to the back boiler I don't believe it can be removed or replaced separately from the boiler.
So the question is - how much more energy efficient would a contemporary combi boiler be and would it be better to replace the existing back boiler with a new combi and a separate gas fire. If a new Combi is going to save me significant sums on gas costs, the extra cost of replacement could possibly pay for itself over the life of the boiler.
Opinions please

Thanks

 

[Last Plumber]

Glow Worm BBU's (back boiler units) Had an efficiency of around 78%. New combi will be late 80's so you'll save around 10%. If you add the right controls, a bit more saving. Especially with weather comp (outside sensor type).
You may save gas on the way things are used too. Heating water as it is needed for example.

I would guess you could save 10-15% on the right job so work out the saving per annum on gas and you'll have a good idea.

You probably won't be able to replace the fire front.

The noise is probably not something a flush will shift.

Hope this helps.

 

[AndrewHarris]

Glow Worm BBU's (back boiler units) Had an efficiency of around 78%. New combi will be late 80's so you'll save around 10%. If you add the right controls, a bit more saving. Especially with weather comp (outside sensor type).
You may save gas on the way things are used too. Heating water as it is needed for example.

I would guess you could save 10-15% on the right job so work out the saving per annum on gas and you'll have a good idea.

You probably won't be able to replace the fire front.

The noise is probably not something a flush will shift.

Hope this helps.

Glow Worm BBU's (back boiler units) Had an efficiency of around 78%. New combi will be late 80's so you'll save around 10%. If you add the right controls, a bit more saving. Especially with weather comp (outside sensor type).
You may save gas on the way things are used too. Heating water as it is needed for example.

I would guess you could save 10-15% on the right job so work out the saving per annum on gas and you'll have a good idea.

You probably won't be able to replace the fire front.

The noise is probably not something a flush will shift.

Hope this helps.

Thanks for this, much appreciated.

Andrew