Had the same on my Strad and again turned out to be the battery. Phew.
Probably sulphated as I suspected on the shelf reducing its capacity to deliver current. Good on the shop, in refunding your moneyJust checked the date on the Yuasa battery that was fitted and suspect I have the source of the problem. I can't see a manufacturing date, but the battery has stamped on it a "recharge due" date of September 2016. Considering that it was fitted as a 'new' battery in August 2018, that might well have something to do with the problem I had. Lesson learned - will be checking dates on batteries in future!
As I say above, there was no quibble from the supplying dealer, Hills of Lymington, on refunding me the price of a new Bosch battery.
Cheers, was just about to pull the trigger on a Bosch S5 019, is this better then? The price certainly is lol!This one, its been brilliant:
The EA1000 Exide Premium Car Battery 017TE is from the Exide Car Batteries range of Car Batteries. We aim to sell all of our products at the LOWEST PRICES in the UK and offer nationwide next day delivery.www.tayna.co.uk