Hi;
I'm an expert PHP developer over 15+ years of experience.
I reead your brief - most people dont, at least, carefully:)
Well, I can see the site you give reads the postcode, but I cannot figure out how do they use the daat in the site? or, how will you use it? For example, will you show content based on this data?
Also, direct matching from a spreadsheet is very very bad idea - reading a spreadsheet everytime when someone connects is super RAM intensive approach, will be very slow and cause too much disk activity, especially if your server have shared disk, or mechanical disks with cheaper SATA connection, or lower end SSD's which have limited IO rate.
A better idea would be is to read the data into a DB table, and match it from there, and maybe update from time to time, depending on update interval of the spreadsheet.
I''m ready to discuss the project, as I'm not sure how complex it is, because still have no idea what you need it for.
I can definitely finish the project - but I'm not a newbie and plan ahead with the every aspect of the project, rather than band-aid solutions like installing horribly coded generic plugins.
I will happily discuss your needs and answer your questions!
Best regrads,
Baris