As well as housing, complaints about asylum, immigration, visas, passports and citizenship are also very common when people come to me for help.
You may find it more beneficial to approach an immigration lawyer, who will be well placed to cut through the bureaucracy of these kinds of cases, but there are also steps you can take yourself.
Before I go any further, if your complaint is about a holiday visa being denied, please be advised that there is no way to appeal this other than to provide that due process was not followed in law, which you will need legal assistance with.
Details of how to complain and the procedure to follow can be found here: https://www.gov.uk/government/organisations/uk-visas-and-immigration/about/complaints-procedure.
For complaints about the Passport Office, please visit: https://www.gov.uk/government/organisations/hm-passport-office/about/complaints-procedure.
If you are not satisfied with the response you receive, they will give you details of how to appeal.