Sorry for the late response - I was quite busy and somehow missed the button to page 2.
Even after performing multiple resets, the WorldSpot firmware was still giving me a lot of trouble and kept pushing Chillispot Config errors (as mentioned in the previous post). In a hurry I missed your reply on the 2nd page and proceeded to seek alternative options.
Fortunately, I reverted back to DD-WRT (latest build, was initially running an older build dated from 2013 that worked for a year) and replaced Google's/OpenDNS Servers with ISP recommended and surprisingly everything is back to normal and working perfectly fine!
To be honest, though I do understand how Google's DNS yields a very long response time, I still don't understand how this issue arose after working fine for more than a year. I was using the OpenDNS servers recommended by WorldSpot all this time and for this issue to occur out of the blue got me very confused. So how can various DNS servers suddenly refuse to work with WorldSpot?
Anyhow thanks very much for your help - everything is working fine after more than a month of downtime. Let's just hope nothing does goes wrong