If you have the standard wave cassette then the boost units will not go straight in, you will need a wiring conversion kit from Mini.
The is a lot better choice in the aftermarket & they play MP3, WMA etc & are far more expandable
http://www.newministuff.com/new_mini_stereos.htm for just a few

 

Cheers Mikey.
If I go for an aftermarket player, would I only need the adapter from the stereo to the wiring harness?
Is this the same conversion kit that's required for the Boost?

 

Different conversion, wave to boost is only available from Mini, think its about £40 you will find a recent thread about it on here.
To go wave to aftermarket you need a wave fiiting kit - £23 from me

 

You have a huge choice if you go aftermarket and there is a lot of
excellent HU's out there. With the kits sold by mickeythemini and
others fitting is easy. There is even a good guide in the FAQ section
which will help you with taking the old unit out and putting the new
in. It is no more difficult than upgrading to a MINI unit. You will also
need an aerial adaptor at £9 which you wouldn't with a MINI unit.
If you have MFSW you will need another adaptor for that and this
will restrict the aftermarket head units you can use. Go on to
mickeythemini's site for information on what can work with the
MFSW. You don't have to use the MFSW though as many HU's
come with a remote control anyway. With aftermarket you'll get
a bigger choice with nearly all being more flexible for any future
upgrades and arguably better sound per pound. Stick to MINI for
looks that integrate well and don't draw attention to thiefs. IMO the
stock speakers are good and will benefit greatly from a better HU.

 

Cheers guys,

That was my next query ,regarding the MFSW. But now all the questions are answered & I now have to make a choice!!