Don't get me started! DCC is the ONLY way to run model trains as far as I'm concerned..... I bit extreme maybe but have said it a thousand times, if it had'nt been for DCC I would never have returned to the hobby.
Anyway, yes it's easy to change a layout from DC to DCC at a later date, in the wiring is less complicated. DCC just requires that there is power to ALL parts of the layout at all times, there is no need for isolating sections or sidings.
Murphy's locos are easy to fit with DCC as they all have sockets for a decoder. Suitable decoders can be got for around the €20 mark and you can get small discounts from suppliers if you but them in bulk.
As for controllers the Hornby Select is ok to start with and will run trains fine but it is very limited in its functions and programming, I would advise that you buy a good controller from the start. As NIR said Lenz are excellent but also very expensive. The NCE Powercab can be got for just under €150 online and will do pretty much all you will ever need.