All of your DNS records look ok
dig +nocmd smilespowder.com any +multiline +noall +answer
smilespowder.com. 857 IN A 188.8.131.52
smilespowder.com. 86057 IN NS ns2.creativelaundry.co.uk.
smilespowder.com. 86057 IN NS ns1.creativelaundry.co.uk.
smilespowder.com. 857 IN MX 0 mail.smilespowder.com.
dig +nocmd www.smilespowder.com any +multiline +noall +answer
www.smilespowder.com. 1198 IN CNAME smilespowder.com.
and you have a redirect in place to redirect non http to https
curl -I http://www.smilespowder.com/
HTTP/1.1 301 Moved Permanently
Date: Fri, 17 Jun 2016 18:41:44 GMT
Set-Cookie: wfvt_3106908635=57644469cc585; expires=Fri, 17-Jun-2016 19:11:45 GMT; path=/; httponly
Content-Type: text/html; charset=UTF-8
I throttled my speed to 2G speeds and didn't get any type of error either.
However, I did notice that the Nameservers you have listed are not valid and the root domain
creativelaundry.co.uk doesn't show the subdomain as created either.
dig @184.108.40.206 +nocmd ns1.creativelaundry.co.uk +answer
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 23902
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;ns1.creativelaundry.co.uk. IN A
;; AUTHORITY SECTION:
creativelaundry.co.uk. 587 IN SOA ns41.domaincontrol.com. dns.jomax.net. 2016050400 28800 7200 604800 600
;; Query time: 29 msec
;; SERVER: 220.127.116.11#53(18.104.22.168)
;; WHEN: Fri Jun 17 13:57:40 2016
;; MSG SIZE rcvd: 114
Personally i would set up a cloudflare account, change your nameservers and let cloudflare handle your dns. I would assume your nameservers not resolving has a big part to play in your intermittent troubles.