Is it advisable to mix different compaines products, say a laney head with a warwick cab? And for £500 would a combo be a better choice than a head and cab?
Depends what combo, what head and cab, but yes it's perfectly advisable, just make sure you use the right resistance cab with the correct head....OR BOOM!!
Yes, it's fine. As long as they match up with wattages and the cab's ohmage is higher or equal to the minimum impedance of the head.