Just went to collect mt tab - note attached to it saying no problem found!
So I went into flipboard and clicked on a website link, set the default to chrome, exited and went back in - it asks me to set the default browser every time. Still a problem.
I also opened facebook and once loaded, scrolled up a down and the lag was very evident. That was after a factory reset and a fresh install by the Samsung approved repair firm.
Handily it did all this in front of the shop assistant. So we went up stairs to look at a shop demo unit, and it ran smoothly and the default browser setting worked once cleared from memory.
So as it turns out, there appears to be devices with this issue, and others that work fine.
I was subsequently given a brand new one after almost 3 months of problems. I hope the new one performs as the shop device did. I suspect a technical issue with the cache memory but then again, at least its not firmware related.