I have a general investment account (stocks and shares) and ISA managed by an investment advisor. I have requested total withdrawal about 1 month ago to fund a property purchase. The ISA was transferred to my bank account fairly quickly, but no sign of the GIA (which held 80% of the total investment value). After a couple of weeke of chasing it, the investment company said that the investment platform (it’s a different company) admitted that they had problems with their systems which had delayed my stocks and shares withdrawal. Basically their system did not log my request when it was sent, and only logged it properly when it was chased 2 weeks later. They apologised 
but the fact is, the value of the stocks and shares fell drastically from the time when it should have been withdrawal to now, which means I will lose about £4K due to their mistake.
They’ve logged my complaint through their complaints procedures. I could not find a compensation policy for this company online, but I made it clear in my complaint that I am being financially disadvantaged due to their mistake and expect that they compensate me for it.
Is there a legal avenue to get compensation if I don’t get it via their complaints procedure?