With regards to bike shops, not all are equal in terms of service. Ask for recommendations from any local cyclists you know. That applies for Halfords too, some a great, some I'm told are awful.

On the Planet X front, I've had repeated irritating experiences with them. Mainly around items showing as in stock but with a vital 'bit' actually out of stock rendering it all a bit useless. In my case the frame was in stock, but the gear hanger was not. After 4-5 weeks of repeatedly being promised a it will be delivered I cancelled my order and ordered a Kinesis instead. I've had other negative experiences with them with other 'attempted' orders. Similar stories really, items not actually in stock and actually on a boat near Singapore. That said, if it's in stock, it's great value and I know a lot of happy punters who have their kit. But my experiences are shared by friends.