The move from climbing to surveying can be a natural one for many. Your experience will give you a gut feel for the health and probable safety of a tree and if you love being around trees this role is a great way to do that from the ground.
You can choose from amenity surveying as a Tree Officer or utility surveying on the national road, water and rail networks and between local authority or private work.
You'll usually need minimum Level 3 in Arboriculture, unless you've been doing it for decades without and have a PTI, so it's worth considering starting a distance learning course before you make your move. These days if you have a good base of arb knowledge you may be able to go straight for a Level 4, which will usually take 2 years distance learning but you'll need to check with your nearest course provider. Treelife, amongst others, offer this course and would be happy to advise; you can read more on this here.
There are other short courses that you can take to bolster your chances, for example:
The QTRA is a recognised methodology it's worth considering.
Surveying Trees for Bats courses will be a good addition to the CV.
There are other short courses you can consider here, many of which have equivalents offered by other providers.
The LTOA (London Tree Officer's Association) have published an informative leaflet about Tree Officer roles, which you can read here.
If you're interested in this career move, please let us know, we've often got roles of this nature to fill.