I tried all the usual suspects, they were all over £200 more than apple at the time.
Like I said, check all the options, don't automatically dismiss apple as the expensive one.
I'm surprised at that, normally it's very much the other way round.
Anyway all MacBook pros are easily upgraded with 3rd party memory and/or HDs/SSDs.
MacBook Airs are completely non upgradeable - although unofficial, and hard to come by, solutions exist for upgrading the SSD (which is dead easy to do, providing you have the correct size pentalobe screwdriver to hand), there is currently no way of upgrading the RAM as it's hard soldered to the main board.
With Mac Minis it's easy to do the RAM, but gets a tad more complicated for the HD. Nevertheless it can be done without any side effects.
With the current iMacs RAM is easy, but realistically you can only build in another apple HD that's been specified for the iMac. Why? well Apple now has special firmware installed on the drives it buys from seagate, WD etc. This firmware allows the use of 2 unused pins on the SATA power connector for monitoring the drive temperature without having to rely on obtaining this info from the drives SMART system, which if regularly requested can reduce disk performance.
The upshot of this is that if you build in a vanilla drive the computer will still function, but the fans in the machine will gradually ramp up until the iMac sounds like a wind tunnel. It's possible to get round this by shorting out two pins on the logicboard's SATA power connector (seriously not recommended), or through software the reprograms the System Management Controller (better, but you really ought to know what you're doing before using this as a solution). Some firms have started to offer hardware solutions to this problem which send the right temperature information to the logic board.
While from an engineering point of view this may be seen by Apple as an elegant solution, it basically screws people who want to upgrade, or who need to replace the HD should the computer be OOW. In fact many industry watchers (myself included) view this as a step further towards Apple's desire to completely lockdown hardware & software, and as a cynical attempt to prevent basic repairs being done with anything other than expensive proprietary hardware.
Mac Pros are again dead easy to upgrade. It's even possible to upgrade the processors in a Mac Pro, although Apple will tell you it's not possible, and it will certainly invalidate your guarantee should you do this.