Not sure what 'wholly ant' travel is, but an employee can only deduct expenses 'wholly exclusively and necessarily' incurred for the purposes of the employment. The 'necessarily' bit is the killer - wanting that bit of extra comfort you get outside Y isn't good enough. The HMRC rule of thumb is: if it was a proper business expense the employer would have paid for it. Accordingly very few deductions for amounts incurred by the employee are permissible.