The following (in no particular order) will sort most issues....
Most of the water sections I came across had the temperature and flow regulators but they were often seized and made little if any difference to the basic operation of the pin. However, unscrew the venturi and clean off any scale...
J&S specialise in warm air systems but got into combis in order to survive as the warm air market gradually becomes obsolete.
They are a very low volume boiler manufacturer (with not a great reputation afair) and few engineers will want the hassle of dealing with them.
That heat exchanger is a...
Low head F&E systems are often problematic and should be ditched in favour of sealed system...is the boiler not approved for sealed systems? There must have been a very good reason to not seal it.
AAVs are plain trouble. Replace with manual vents...I use the 1/2 radiator type vent with a 1/2 BSP...
I'd run it close to maximum...you don't want it condensing much given its age and parts availability.
It's nearly 20 years old, unlikely to have ever had a proper service (and it's impossible to fully clean the recuperator due to the design and it could be very corroded by now)
The sump gasket...
We're living through one of the most unstable periods in history....suppose the markets started to tumble how confident are all you online investors that you could pull your money out or switch into safer stock? Will your trading platforms hang under the severe pressure? The city will have...
The seller lists it as new but the description tells you it's "refurbished".
This dishonesty is now common on ebay (along with society in general).
Only buy brand new in box where you can clearly see the part no. etc.
There are 2 types of hex fitted to this boiler depending on the condensate...
The ribbing is caused by the aluminum spiral formed on the outside of the casting expanding to the point that it stretches the stainless steel jacket.
It's not that unusual but suggests the boiler is running a little too hot...plenty of boilers have it with little issue.
However, overheating...
There is no such thing as a reconditioned primary heat exchanger for this model....the o ring (the seal that has leaked on yours) is not accessible.
Any 2nd hand/reconditioned part could fail in exactly the same way within a short time. Furthermore you can't recondition aluminium alloy that has...
Unless there's a very good reason the pump should be on the flow to ensure the highest pressure at the radiators.
Why is the fire valve not located outside?
Surely the installer didn't leave that capillary and cabling in that state...
Many policies (mine does) have clauses that specifically void the policy for negligence eg. felling trees without appropriate training & qualification could be deemed as such.
Be aware that many meter adapters have single or double checkvalves built in.
I don't know whether they are accessible to clean out but it's likely they will be full of debris too.