Looks like the intermediate certificates are out of order, and gnutls doesn't like out of order certificates (cert #1 and cert #2 are inverted):

mdeslaur@mdlinux:~$ gnutls-cli --insecure --x509cafile /etc/ssl/certs/ca-certificates.crt --print-cert -p 443 www.securesuite.co.uk
Processed 153 CA certificate(s).
Resolving 'www.securesuite.co.uk'...
Connecting to '62.73.172.27:443'...
*** Verifying server certificate failed...
- Ephemeral Diffie-Hellman parameters
 - Using prime: 1024 bits
 - Secret key: 1022 bits
 - Peer's public key: 1024 bits
 - PKCS#3 format:

-----BEGIN DH PARAMETERS-----
MIGHAoGBAKUEMpwau6Vsvv2NV4gRFc/E5p0Gxydj2S/+3bqqc6CM7Uy1Y1eZeSC6
5FQLN04IIfusxDi5nX5DvC3CaD3u7899ixFFkBd7OsS7F1dIgTzr3+2rWicMULxV
T2RQE2y4wsvt1S47hxuDrxkUn0bFwO/KukaR5NRZ7L5Guj/VIG47AgEC
-----END DH PARAMETERS-----

- Certificate type: X.509
 - Got a certificate list of 3 certificates.
 - Certificate[0] info:
  - subject `C=US,ST=Massachusetts,L=Bedford,O=RSA Security LLC,OU=Verified by Visa,OU=Terms of use at www.verisign.com/rpa (c)05,CN=www.securesuite.co.uk', issuer `C=US,O=VeriSign\, Inc.,OU=VeriSign Trust Network,OU=Terms of use at https://www.verisign.com/rpa (c)10,CN=VeriSign Class 3 International Server CA - G3', RSA key 2048 bits, signed using RSA-SHA1, activated `2011-08-22 00:00:00 UTC', expires `2017-08-20 23:59:59 UTC', SHA-1 fingerprint `771ef15fe1aae19c9c204a3bc59d14dea39bd85c'

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

 - Certificate[1] info:
  - subject `C=US,O=VeriSign\, Inc.,OU=VeriSign Trust Network,OU=(c) 2006 VeriSign\, Inc. - For authorized use only,CN=VeriSign Class 3 Public Primary Certification Authority - G5', issuer `C=US,O=VeriSign\, Inc.,OU=Class 3 Public Primary Certification Authority', RSA key 2048 bits, signed using RSA-SHA1, activated `2006-11-08 00:00:00 UTC', expires `2021-11-07 23:59:59 UTC', SHA-1 fingerprint `32f30882622b87cf8856c63db873df0853b4dd27'

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

 - Certificate[2] info:
  - subject `C=US,O=VeriSign\, Inc.,OU=VeriSign Trust Network,OU=Terms of use at https://www.verisign.com/rpa (c)10,CN=VeriSign Class 3 International Server CA - G3', issuer `C=US,O=VeriSign\, Inc.,OU=VeriSign Trust Network,OU=(c) 2006 VeriSign\, Inc. - For authorized use only,CN=VeriSign Class 3 Public Primary Certification Authority - G5', RSA key 2048 bits, signed using RSA-SHA1, activated `2010-02-08 00:00:00 UTC', expires `2020-02-07 23:59:59 UTC', SHA-1 fingerprint `b18d9d195669ba0f7829517566c25f422a277104'

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

- The hostname in the certificate matches 'www.securesuite.co.uk'.
- Peer's certificate is NOT trusted
- Version: TLS1.0
- Key Exchange: DHE-RSA
- Cipher: AES-128-CBC
- MAC: SHA1
- Compression: NULL
- Handshake was completed

- Simple Client Mode: