BB Bold 9700 :: Email - Business Account Email Does NOT Arrive On Device

I hope someone can help because I'm losing the will to live over this one!

Device info
Your carrier: o2 UK
Model info and OS version (Go to Settings, then Options, then about): Blackberry 9700 v5.0.0.321 (platform 5.1.0.90)
Apps and free space
File free before and after a battery remove/replace. (Go to Settings, then Options, then status): 128872013 bytes
Did a battery pull fix your issue? No

I bought a SIM free BB 9700 to use with my 02 SIM card. I applied the unlimited BB tariff and proceeded to set up four email accounts into the device which are all for my small business. I waited to do this until I knew the O2 bolt on had been applied correctly.I set the accounts up via the BIS server website which sent them down to the device; seemingly correctly.

I received email correctly for that day and could send as well with everything syncing with my IMAP servers and Outlook.Next morning - no email delivered to the device and I was unsuccessful in sending emails as well from the device to addresses.I tried to send down the service books - I sent them but no change.I got my four email accounts working again correctly but had to delete the accounts from BIS and recreate.I could then receive email correctly for the rest of the day and could send as well with everything syncing with my IMAP servers and Outlook.

Next morning the same thing happened - no email delivered to the device and I was unsuccessful in sending emails as well from the device to addresses.I then did a complete device wipe.When the device rebooted it seemed to synchronise with the BIS and then my accounts worked again for the remainder of the day.This morning - the same thing happened - no email delivered to the device and I was unsuccessful in sending emails as well from the device to addresses.

I have now created my @o2email address and applied my long standing @hotmail.co.uk address to the 9700 and they work fine - at the moment (we'll see about tomorrow!) to see if they fail as well.I have sent test mails today from the @O2 account and hotmail to each other and also to my main small business account from my BB. The @O2 and Hotmail emails arrive both on the device and (hotmail) on outlook and the main business account arrives on outlook BUT the main business account email does NOT arrive on the device.

I cannot seemingly send anything from my business addresses anywhere (from the device) with the only outgoing addresses that work being the @O2 and @hotmail accounts on the BB - unless I do a device wipe or delete the accounts and recreate.Emails sent from the BB from either @O2 or @hotmail arrive on the BB but not anything sent to the work accounts sent from @O2 or @hotmail from the BB - although the emails sent to the work addresses WILL appear on my outlook...

Speaking to O2 has been tough and they are blaming the server people who host my small business domain and such, although I think it is more than that though I could be wrong.My server people insist it isn't their end, saying they can see from the logs that RIM seems to stop checking for emails at times they detailed when the device stopped receiving emails from one day to the next.