You can bring legal action in the family court in Israel for a Hague Convention order for the return of your abducted son to the U.K. By retaining your son in Israel against your wishes, and not returning him to his country of habitual residence, your wife is acting unilaterally and wrongfully, and committing a form of passive civil child abduction. Both the U.K. and Israel are bound by a convention covering international child abduction and there is a special fast-track legal process for filing for an order for his prompt return.
After you file in court, there may also be the opportunity to negotiate a voluntary return, without the case running the full course. Though it is extremely rare for there to be marital reconciliation after a scenario like this, it is possible. For example, our office represented a father, whose wife refused to return to the U.S.A with their children at the end of the school vacation, in the Summer of 2014. After filing Hague proceedings, at Tel Aviv Family Court, the parties reached agreement for a voluntary return. Within a matter of days, the wife and children flew back to the States, the Hague file was closed, the family reunited, and the marriage reconciled (File 13200-08-14).