Very generous offer. In the interests of completeness please note that upon return to the UK VAT will need to be paid as Rolex and Tudor are duty free at LHR meaning you will be above your duty free limit on return. This differs to all the other brands which are discounted by the amount of VAT but have VAT paid and are therefore fine to bring back without further payment.
Would hate for anyone to get in trouble and they do check now very frequently