you can have multiple certs but they need to be assigned to different vserver.
So, you need to be able to distinguish between the 2 at TCP/IP level.
Either by ip address or by tcp port.
ie: test.com will be on x.x.x.x:443
test.uk will be on x.x.x.x:444
or
test.com will be on x.x.x.x:443
test.uk will be on y.y.y.y:443
This is true for any loadbalancer.
Since you need to know which cert to use decrypt the traffic and only when the traffic is decrypted can you see the http header that contains the hostname.
Gilles.