a service dog for ash

my son ash has severe autism and tourettes, he can't go to a normal school, he can't go for a normal family day out, he is allowed a service dog which would mean he would hopefully sleep at night as he is scared of every little thing, he would be able to go out as a family without risk of him running into roads, hopefully it will stop him hurting himself. the only problem is it costs £5000. We don't have that sort of money so we are begging people for their help, to give our son a life.