Normally the best advice seems to be to save as
much as possible in an AVC scheme and then look
elsewhere for tax breakes...Possibly an ISA?
With a pension/AVC your contributions are made
before tax (eg you save tax now) but you will
probably pay tax on your final pension income.
With an ISA you make contributions out of taxed
income (eg save no tax now) but you may be able
to get tax free income in retirement (for example
by regularly cashing in investmants that have grown tax free).