Some advice choosing new mountain bike please?

[fritz_le_cat]

Insurance are replacing my stolen bike with a £550 Halfords voucher. Don't use/need the bike for off road. But would like to get a lightweight, front suspension, front disc brake mountain bike. (Hoping i can get a £300-£400 bike, with credit note for rest...) Should i go for hydraulic or cable brakes as regards maintenance? As rim brakes on the rear seem like the best hassle free option, should i actively stay clear of rear disc option? Are there any spec's i should look for in front suspension forks? And any reasons to go with a particular brand? Kona or Boardman at the top of price range, Saracen or Carrera at lower end? And finally, any recommendations on either the D-lock, or chain and padlock as most secure option? ....Too many questions above, so if you recommend, suggest or advise on one, cool. Thanks for all ideas/info.