Proper AV fellow, checkatrade and all that! I have ordered a cable tester, should arrive tomorrow. Spoken to the contractor as well, he's gonna discuss tomorrow.
By rights (doing things correctly/by the book):
1. Fixed building structured cabling, is much like electrical cabling, in that it is solid core (not stranded). Therefore it should always be terminated/punched down onto IDC contacts on either RJ45 jacks/sockets or RJ45 patch panels (or if your really old fashioned like me 110 style panels). Most folks especially in residential settings and especially AV dudes, sparks and mom and pop/DIYers ignore this and crimp an RJ45 plug onto the fixed cabling. This saves time/money blah blah but isn't the best long term especially if that solid core cabling gets moved about - it can eventually break internally - which is why....
2. Fly-leads / patch cords are known as "work area cables" they use a stranded core construction, which makes them nice and flexible. They are designed to be bent, twisted and generally [censored] about by end users ands still work for years.
3. A good installer always tests every fixed cable that they install. No one is perfect and structured cabling is very easy to fudge up. A really kosher installer will use a performance tester to ensure the cabling meets EIA/TIA Category standards (or the ISO equivalent Class) - however given that Fluke testers are the better part of £10K and most installers that do residential installs won't have the turnover (or expectation form their clients) for this level of gear.
They could however do a continuity test which is quick, cheap, easy and eliminates 90% of faults.
Hope its all works out well and its made good.