The kit itself wont sell too fast anymore as its really outdated, not many lining up to fit a 15 year old system into the car but if you break it down into individual pieces and list it on ebay you should get decent money from people looking for replacement parts

Depending on the parts
Mk 4 nav £150-200 /mk3 £80-100
16:9 screen £100-125
Bm54 module £125/ bm24 £50
Tv unit £20 if even
Loom £50
Ulf module if present £75-150 depending on gen

Best market for them ebay.uk