Hi,
Thanks for that clue podilarius, after looking at the state table I noticed ICMP packets from pfsense to the 192.168.3.1 WLAN router were going via the LAN 192.168.0.1 vip.
This led me to the Manual Outbound NAT rules and I had a rule there saying:
"WLAN 192.168.3.0/24 * * * 192.168.0.1 * NO" (WLAN to vip1 LAN)
Removing this fixed it!
I had to remove stale states from the state table manually too for changes to take effect immediately as the gateway status still showed the 192.168.3.1 router as being down (through apinger).
I also didn't have a default gateway set on the backup so setting that fixed the routing tables.
And on a slightly different note, my 192.168.2.1 adsl modem/router didn't pass multicast over it's switch (they're just getting too clever and locked down these days!) so I had to put in another unmanaged switch inbetween to allow vip2 interfaces to switch from master->backup properly, (as stated in the sticky, but I had to read that more than a few times before it sank in!)
Looks like it's ok now, thanks for the help!
Best Regards,
Vent