You can get a 'Tree Surveyor' in, but this costs money. I have no idea how much. You can always enquire. They make a survey of the tree specifically with safety in mind.
You could get a tree surgeon in to do a site visit with a view to quoting on work that they feel could be done on the tree and they will likely tell you what they think of the tree and make suggestions. This site visit should be free. Tree surgeons will tell you though that they are not formal tree surveyors and that they are not insured to provide official safety advice. Also bear in mind that their advice may be biased by the fact that they could benefit financially from the work they tell you needs to be done on your tree. Also Steephill rightly said, the tree surgeons first question will be, "Is there a Tree Preservation Order on this tree?".
It may also be a good idea to pose your question to the Woodland Trust who may also be able to advise. Here's their website: https://www.woodlandtrust.org.uk/
Best of luck - would be interested to hear what happens...
The Grateful Deadhead