iRule Syntax error

What syntax error are you getting? Also, try using some

string tolower

and

HTTP::path

rather than URI because that will include the query as well. Also, you are probably better off with

starts_with

unless you want to match the path exactly. Also, you may be better with a switch rather than all these ifs.

when HTTP_REQUEST {
    if { [HTTP::header "User-Agent"] contains "Windows " }{
        if {[string tolower [HTTP::path]] starts_with "/checkversion"}{
            HTTP::redirect "https://test.co.uk//deposit/registered"
            log local0. "https://[HTTP::host][HTTP::uri]"
        }
        elseif {[string tolower [HTTP::path]] starts_with "/register"}{
            HTTP::redirect "https://test.co.uk//signup"
            log local0. "https://[HTTP::host][HTTP::uri]"
        }
        elseif {[string tolower [HTTP::path]] starts_with "/forgotPassword"}{
            HTTP::redirect "https://test.co.uk//forgot-password"
            log local0. "https://[HTTP::host][HTTP::uri]"
        }
        elseif {[string tolower [HTTP::path]] starts_with "/logvar/address-json"}{
            HTTP::redirect "https://test.co.uk//cashout"
            log local0. "https://[HTTP::host][HTTP::uri]"
        }
        else {
            HTTP::redirect "http://test.co.uk"
        }
        log local0. "https://[HTTP::host][HTTP::uri]"
    }
    else {
        HTTP::redirect "http://test.co.uk"
        log local0. "https://[HTTP::host][HTTP::uri]"
    }
}

or

when HTTP_REQUEST {
    if { [HTTP::header "User-Agent"] contains "Windows " }{
        switch -glob [string tolower [HTTP::path]] {
            "/checkversion*" { HTTP::redirect "https://test.co.uk//deposit/registered" }
            "/register*" { HTTP::redirect "https://test.co.uk//signup" }
            "/forgotPassword*" { HTTP::redirect "https://test.co.uk//forgot-password" }
            "/logvar/address-json" { HTTP::redirect "https://test.co.uk//cashout" }
            default { HTTP::redirect "http://test.co.uk" }
        }
        log local0. "https://[HTTP::host][HTTP::uri]"
    }
    else {
        HTTP::redirect "http://test.co.uk"
        log local0. "https://[HTTP::host][HTTP::uri]"
    }
}