Just ask for reimbursement via the Complaints portal, there is a particular tab for expenses. If the hotel costs a lot more than £200 per night and there are other mid-range hotels under £200 then it is worth considering a move. It's not likely to be turned down, it's covered by both EC261/APR and the Israeli version. More details in the main EC261 thread, and note also the FAQ signposts thread for irrops and delays. However if it is a silly amount BA have been known to be slow to pay / need escalation.