I got mine in 25 minutes and it only took that long as the guy kept asking for my father-in-law to come and pay a fine as he'd never seen the online TM30 PDF before. I kept pointing to it eventually he took it to the back office and came back and said ok. 555
For foreign Visas all an agent can give you is the experience of doing the process and getting it right first time, seems like you were very unlucky and chose a bad one. As above if it's online try yourself as you will have gathered most of the documentation required. I hope you were not charged by the agent btw as it should be no visa, no fee.