In the vast majority of cases where there is a non-professional executor, they do not claim expenses which is probably why the solicitor was surprised. That's why testators appoint family members or friends rather than professionals who might do a better job of it but be more expensive. For eg if all testators appointed accountants or solicitors or indeed, in your type of circumstances, private detectives, probate would be much more efficient in general. Testators tend to think their executor will do it for 'love' not money.
As the executor you are entitled to claim your 'reasonable' expenses. As the executor you are also entitled to decide what is reasonable. The buck stops with you. If any of the beneficiaries afterwards think that your expenses were not in fact reasonable then they could take a claim against you as your responsibility is to ensure the best for the beneficiaries and clearly if you take too much as expenses that wouldn't be the best for them.
So at the end of the day it's up to you.