Lenovo's UK support phone number is 0333-777-3991. Lines are open from 0900 to 1800, Monday to Friday. Calls are charged at the same rate as 01 & 02 numbers, from both landlines and mobiles. (That might well mean that the call will be free to you if, say, you've got a mobile plan which gives you free minutes).
There might be additional support options shown via this link but, because you have to enter your laptop's serial number, I can't see them myself:
https://pcsupport.lenovo.com/gb/en/contactus
However if the password you're seeking is a Windows one it's unlikely that Lenovo will be able to access it anyway. You'd need to use password-cracking software, loaded onto a USB stick, in order to find it. Any decent computer technician should be able to do the job. (It can be done yourself but you need to be technically-minded, as it involves things like BIOS settings and ISO images, which can take a bit of getting to grips with for a novice).