456GT Washer pump

You may be able to access it via the wheel arch. i.e. remove the wheel and the liner. If you have to remove the tank, just be aware these tanks are fragile and crack easily.

Perhaps there is alternative access by removing the underbody panels?

 

Remove the front undertray around the bumper. You will have full access from there. You should be able to pull the pump without removing the tank. I would first out 9v to the pump to see if thats truly where your issue is. On my car i found one of the lines up towards the windshield and under the cowl is pinched and hardened making flow out to the sprayers nearly impossible, yet very tough to reach where it sits.