Actually believe the UK does provide such but has to be asked for (at least that was the old system from reports). 90 day reports can normally be done online for many people. As you used an agent check where the extension of stay was issued - it may not be from your local office making transfer tricky for the agent. I would seriously consider starting over using a new passport entry without agent if you can qualify for extension, they are not hard to do if you meet the financials. A bit concerned about the second reference to agent having passport - are you talking official UK facility or another JoeBlow? Although it may only be a gray rather than black option highly advise against using someone that can disappear in the dark of night.