It has been suggested that the right to paid holiday could be diminished following Brexit.  This is because the right to paid holiday in UK law comes from European legislation.

However, although it is possible that this could happen after Brexit, my personal view is that any changes will not be immediate and if they happen they are unlikely to significantly disadvantage UK workers.  This is because the UK actually goes further than the EU by specifying that full time workers are entitled to 5.6 weeks' paid holiday whereas their entitlement under EU legislation is only to 4 weeks' paid holiday.

The suggestion that part-time workers could particularly be affected is possible, but I think also unlikely because part-time workers' rights are now entrenched in UK law and there remains the risk of sex discrimination claims should part-time workers' rights be detrimentally affected.  This is based on statistically more part-time workers being female than male (although it is possible this could also change).

The right to paid holiday has become complicated by EU case law which means that in many instances overtime pay should be taken into account in calculating holiday pay, but this is only required for the first 4 weeks of holiday entitlement.  We do not know what will happen after Brexit, but I would have thought that if anything changes, both employers and workers could benefit from an opportunity to clarify how holiday pay is calculated.