An Impact Assessment on the wider impacts of the ending of free movement for EEA and Swiss citizens was laid alongside the Immigration and Social Security Co-ordination (EU Withdrawal) Bill. It can be found at https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/885682/2020-05-18_IA_ImmSSC_Billl_v21_with_Signature.pdf
On 19 March 2020 the Home Office published a literature review of the evidence relating to the elasticity of demand for visas in the UK. This evidence is available here: https://www.gov.uk/government/publications/a-review-of-evidence-relating-to-the-elasticity-of-demand-for-visas-in-the-uk
The impact of the imposition of both visa fees and the Immigration Health Surcharge on EEA and Swiss citizens will be published alongside the Immigration Rules and Fee Regulations in the Autumn.