[quote name='P_bass_1983' timestamp='1449600561' post='2925070']
...can anyone recommend somewhere (preferably south uk) that would give me good trade in prices or better still, do a 4 for 1 straight swap.
[/quote]
I doubt you'd find anywhere that would do you that deal. Shops have overheads and tax to pay on sales, hence any price offered would be minus tax and the cost for them to have it hanging on the wall (+ the headache if a used bass had an issue when sold). You can generally expect to be offered 25-50% of an instruments worth as a trade in (average used value), you'd get much more selling private!