On 13 March, the Treasury allocated c.£1.6bn to departments on March 2018. A full breakdown of the allocation can be found in the Chief Secretary’s Written Ministerial Statement, HCWS540, laid on the 13th March https://www.parliament.uk/business/publications/written-questions-answers-statements/written-statement/Commons/2018-03-13/HCWS540/.
Details of some of the work done by departments funded by these allocations can be found in the Technical Notices published on 24 August (https://www.gov.uk/government/publications/uk-governments-preparations-for-a-no-deal-scenario/uk-governments-preparations-for-a-no-deal-scenario).
The independent Office for Budget Responsibility as part of their fiscal forecast take a judgement on how much departments will underspend on all aspects of DEL spending. This information is available at https://cdn.obr.uk/EFO_October-2018.pdf.