gone into classic mode

If you're on the 'classic' betfair website, top left hand corner click on the betfair logo (under the yellow go to sportsbook) then right hand side under 'top features' click on betfair community and there should be an option to switch back to the new forum.

I think the OP means the Classic view of the Forum?

In which case the link to switch back is at top-left below Sports, below the Betfair logo

I don't have that longbridge, I just have a band at the top that says Community Classic then y username and below is the forum menu on the left and the forum on the right...

keefter- go to the classic (main) website and follow the above instructions and you can get back to the new forum (no idea how to get back to the new forum from the new website)...or alternatively try clearing history etc and you should get taken back to the new forum by default.

@Keefter - for me, that band with Community Classic etc sits below 5 other bands, so don't know what you're doing different.  Sorry can't help.