When these noises happen - best to develop - if not done already - a maintenance schedule.
To have a mechanic look at it for 90 £ - is a LOT cheaper than to have that same mechanic have to find and fix something that was broken due to not following a schedule and maintain the vehicle.
It also works in your favor as cheap insurance because you have found a mechanic that although may be expensive to you - might be the one that knows more about this condition - or not - so it's best to get second opinions.
You will have to look at your options.
You give us very little information to go on - so you're asking us to pull a rabbit out of our hats...
90 bucks (£)? It' only goes ↑ from here on out...
A simple "tik" every ten seconds can simply be from a purge valve used to pull fumes from the EVAP canister that stores the fumes from the gas tank - as far as being a condition - you say it goes away as you drive. So more than likely it is a valve that has worked its lifetime and is near its end of its life cycle, so it has to be replaced.
You also own and operate a vehicle that is from 2008 - it's now 2023 - nearly 15 years of operation - that's a pretty good score and for you to be upset of a mechanic that costs you money to just take a guess - well, that is your choice - but you do deserve to be congratulated for a feat many overseas here in the US - wish we could still own and have.