If youre getting a club fitting, get a good one, depending on your budget.
The absolute best place IMO is Precision Golf in Surrey. Closer to home, Scottsdale golf in Birmingham build most clubs on the day.
Fitting is a bit of an art rather than a science. it needs some dialogue with your fitter, and it needs some understanding of what youre looking for and what you are trying to achieve.
For example, when people think of a term like "Dispersion" people will immediately think left and right. Not really. YOU are creating left and right dispersion, "Dispersion" really means how consistently does the club retain launch and spin properties depending on where on the face you hit it, and the situation youre in, so as an example coming out the rough you dont want balls that lose spin and fly forever all the time (as an example).
Also, hitting a ball bang straight down a line is a pretty much useless skill, so the fitting needs to take into account what you do in a real world setting, not just indoors.
Be careful as well that when fitting clubs, you CAN be upsold certain options that are doing very little for you. Shafts are an obvious one. Its easy to sell expensive shafts because your Ventus Black and your Graphite Design VR are sexy and masculine....its like BMW's and Mercs. It has a much smaller impact on the quality of your shots than you might think i can assure you, a good fitter will explain this in detail. Its a TIMING DEVICE.
When you hear of a shaft being "high launch" or "low launch", again NO THEY ARE NOT!!! the only way a shaft can make you launch it higher or lower is if the shaft influences THE WAY YOU DELIVER THE CLUB TO THE BALL. Thats not the shaft in of itself doing that, its the effect the shaft is having on YOUR DELIVERY, and that will NOT always conform to the "norms" youve heard before in golf.
Example: Patrick Cantlay uses shafts that are lighter and softer than Colin Morikawa. Patrick Cantlay swings faster than Colin Morikawa, hence he *should* use the heavier stiffer shafts if following that logic. He doesnt.
That all being said, fitting IS essential to improve your golf game as it can really work WITH your swing to make the most of it.
Lessons wont really matter to a lot of aspects of your swing and if your delivery does change a little, you can always bend the lie angles a little flatter or more upright if you need to, but lie angles GENERALLY dont really ever go more than a couple of degrees in either direction (GENERALLY) so theyre not huge changes if needed.
If youre prepared to travel, check out precision golf. They do lots of fantastic youtube content and they are an unbelieveably good fitting centre.