I'm looking at some 14" wheels on 45 profile tyres but I'm worried that I wont be able to have my car rediculously low, anyone got anything similar and how low can the car sit on them?

Depends on rim width & offset and what size tyre?? 45 is a percentage of the width, so without that it's a bit irrelavent

There 7j and the et must be around 20, tyre must be between a 165-185?

Again, 45 is a different profile on a 165 than it is on a 185.

Also, tyre size availability is poor in 14s - if you're hoping to find a 175x45x14 good luck with the search.

I believe you can get 175x50 though and they would be ideal if you can find some.

175/50 is available, bit small circumference wise

185/50 & 195/45 are avail. Both a tiny bit smaller I think but are ok.

However 7" rims et20 may scrape dependant on arches suspension etc

Rears will be fine and front would need camber.