The Benchmark Project
Reference map is https://parallel.co.uk/os-benchmark-archive/
I suggest that you choose 6 benchmarks near where you live and then go for a walk to find them.
If found then take a photograph close up and another showing where it is in a wider view.
Name the images with the name on the Benchmark map such as St Andrews CH E Ang 52.0173m for the church in Laverstock.
If the mark is on private land then you must attempt to contact the owner of the property and ask if they are aware of their benchmark.
Usually you have to explain what it is and roughly where it is on their house. The map says things like NBM NO11 MIDDLE ST N ANG 46.427m to indicate that you should look on the North corner of the house. Looking at it on Street View makes it look improbable. But you never know.
I looked for 6 and found only 2. For 2 marks the owners tried their best to help find it but it has been plastered over or there is an extension.
Another useful website is https://tinyurl.com/y43s224p as it shows types of benchmark that you may find.
Another site is worth reading https://tinyurl.com/yxzjqzc7 giving more background information.
Examples
