I tend to use the following places
  www.aria.co.uk
&
  
www.ebuyer.co.uk
 
 Dabs (now owned by BT) don't seem to have competitive prices anymore
 Plus of course Novatech for things I want today. Order online & collect 
especially convenient if I'm at a customers in Pompey.
The biggest issue with buying stuff online is the delivery. Both ebuyer 
& aria seem to use the same delivery company. If I'm out when they call 
and want to collect from the depot then I have to trek over to 
Blazingspoke which is a real PITA. That said, I know to expect them to 
deliver between 2pm & 4pm in Aldershot.
Aria's next day delivery has been 100% so far.
my 2p worth
Stephen D