Audio advice for my T25 High Top

I have recently purchased my first Camper van, a 1988 VW T25 High Top with Reimo conversion.

Everything is sweet inside bar one important feature....the audio setup!

All that is present is an old sharp radio with one speaker that has been installed underneath the fix on dash board!

So...i have an open canvas as to what i buy and where it goes.

But, i dont know where to start?

If anyone can give me some advice as to where they have installed there speakers, if they have a sub where and how have they put this in.
Im also looking at having an extra set of speakers in the back, possibly in the rear storage cupboard above the chair/bed?

Id be muchly appreciative if you could offer any sore of advice on what kit is hot, pictures of their audoi installation would be wicked too.

Hope you can help

Kidders