There seems to be a bit of confusion regarding this ongoing matter - to put the matter straight, NO ONE needs to exchange their UK Licence until it expires providing the rules regarding medicals are adhered to (first medical at 45, then 55,60,65,70,72 and so on) - if, as has already happened someone is involved in a RTA and the police ask for a licence they will ask for a Medical Certificate (if over 45) NO CERTIFICATE and you will be deemed to be driving with an expired licence, the consequences of which might be - no insurance cover and possible criminal conviction.

Don't take my word for it go the link below which is the European Court Ruling on this matter - note para 3

http://www.spainvia.com/drivelicenceletteradsl.htm