Since you will be migrating from UK, I assume that you folks would be leading a decent life. Although you have not specified anything about the role he is searching for, at his experience, skills, certifications and most importantly the background with which you would relocate, I recommend to ask for at least 25,000 QR per month. Also ask for the educational allowance (in case you have kids), travel allowance (sponsored trip at least one a year to your home country) in addition to 25K amount.

All the best for the job search!