Ok All I thought I might come back to this and provide some more info on how this ended up.
We've minimised the 503 errors, as far we could tell this was being caused by the built-in timeout mechanism of varnish and the solution was not to increase the timeout (tried and it didn't work) but rather to move the site to a better server that could respond faster.
The second issue was the constant being logged out, this was because of incorrect install of the rpaf mod, there are some guides out there in the google-verse that you can find for setting things right on both servers (if you are indeed using separate servers for varnish and your website). Once this was done correctly then IPB worked correctly.
We're in the process of creating translations of our forums at muslimvillage.com/forums in different languages,
the translation is hosted elsewhere such as when someone goes to fr.muslimvillage.com/forums they will get the french version of our site, this mostly so people are able to find our content in different languages.
So far, translations such as french haven't been too bad but translations such as arabic (ar.muslimvillage.com/forums) have been completely unreadable.
I wanted to know if there are settings that need to be changed in order to accomodate this or if it's done elsewhere, we're using a translation service from gtranslate that started in our wordpress main site at muslimvillage.com but carried over into the forums at muslimvillage.com/forums