I think it's unfair to judge a letting agents on a single bad experience, but the sheer number of times Ludlow Thompson have let us down makes me think this is an agency which is frequently incompetent - both on the side of moving into their places and moving out.
We used them for 3 years over two properties (now switched to KFH who, touch wood, seem much better) and while their website is one of the best I've seen, the repeated incompetence of the staff beggars belief.
The main problem seems to be that none of the staff there talk to each other. If you're moving out, you'll get asked whether you plan to stay by at least 4 or 5 members of their staff at different times. This will often be followed by a written confirmation of the exact opposite.
They're also remarkably pushy, frequently ignoring their own promise to give you 24 hours notice for viewings and trying their arm with emotional blackmail about how they really need to show the clients round with 2 hours notice, and so forth. Politely declining these requests is often met with rudeness in return.
But the absolute best example of their incompetence comes from the move between the two flats we've had with them, where they rescheduled our move-in date without telling us, despite this leaving a gap of two weeks between us leaving their first property and arriving at their second. After many frantic phonecalls to them, they eventually managed to close the gap to a single day, but there was no hint of an apology, and you just get the impression that their staff will happily arrange to stuff without checking with the client. They just chance their arm with everything they do - forget about professionalism.
Lots of this stuff is pretty commonplace between agencies I imagine, but my message to you is that the service you end up receiving is often completely at odds with the professional look of the offices and website.
What agent could do to change your mind?
Be more competent and less pushy