If there is a WDA this normally refers to Capital Allowances. Is the client an individual?
If there is a value for depreciation in the accounts under Computer Equipment no cost value to put it against it could have been posted incorrectly.
I would go back to the previous accountant and ask for a breakdown of either (1) Capital Allowances Schedule (2) The Fixed Assets Schedule. This should be given to you as part of the hand over.
Yes, get an explanation from the prior accountants and ask for Fixed Asset Schedule (which should show cost, depreciation and NBV) and as you have mentioned WDA (which refers to Capital Allowances) ask also for the CA Schedule too. This will always be different to the fixed assets which is used in financial accounting whereas CA's is used in computing allowances on assets based on HMRC's "rulebook".