@Solla-topee Thank you for the response, this is one of those times when it is lovely that there are complete strangers around who are willing to offer up their thoughts :-)  

Yes, that's what I thought - two completely different apps. Controlling completely different sets of plugs, what does it matter if the login details were the same.  One the different apps on the phone I can control the two different sets of lights, but yes, installing the two different Alexa skils and assuming they would be able to play nicely together as essentially it should direct two different apps was where it all fell apart.  I had complete control over the Kasa 4 plugs through the Kasa skill all was working well, then I installed the Tapo skill onto Alexa and now all that I have control over is the single Tapo plug I have running (I have another 3 Tapo to set up).  It said the Kasa server was unresponsive for all the plugs from the moment I installed the Tapo skill.  Even when I put in the current Login details and password I can't get into the Kasa plugs on Alexa despite having both skills enabled.  I did wonder if I had two totally logins and two different emails would it work, but I unless I undo the 4 working plugs, get them back to factory settings, then set up a completely new Kasa account under different details I can't see any way around doing it and they are all currently doing things at the moment (though I've had to control the Kasa's today through the Kasa app directly on the phone rather than through Alexa.  I can't even change the Kasa account to a different email address as that seems the primary identifier for the account and you can't change it.  I've tried removing the Alexa skill and reinstalling it, but even when I put in the correct details it says it can't connect to the server right now.  Even if I uninstall the Tapo skill from Alexa it still can't connect to the Kasa server.  

I have now spent about 4 hours fighting with it and am completely cross with the whole thing.  The ironic thing is because I couldn't buy any more Kasa plugs on Amazon I only chose the more pricey Tapo plugs option because it was more TP-Link stuff and I thought it would be easier to make it all work together - if I had bought a completely different system the Kasa plugs would still be working on Alexa - I am very disappointed and considerably frustrated.

 Nope Definitely doesn't want to hook up the Kasa side of things to Alexa.  I keep getting 'the server unavailable at this time please try later'.  Tapo is Alexa hooked, but the Kasa side of things doesn't want to know, yet I can log into the Kasa app itself and see those plugs away from the Alexa app.

Update:  Absolutely outstanding support from TP-Link.  I'm amazed that their engineers responded to this issue directly - certain other big companies seem to completely ignore their forums - yes M.......t I'm looking at you - I got emails, and their support team sorted me out in about 48 hours.  Turned out I needed to link the accounts from within the Kasa app.  To do this meant going through some clicks from the 'Me' icon in Kasa - not something I had tripped over.  I had read that a link might be needed and had previously tried to find it, but the location wasn't easily evident, possibly it would be worth making it easier to find in the Kasa app.?   Anyhow, real people responded, they actually READ my emails and clearly weren't working from a crib sheet of 'let's follow through 50 sets of obviously checks'.  I am now up and running and am delighted.  Well done TP-Link if anything will make me buy more of your products its the sensible and customer focussed support that you have provided :-)  Thank you!