Diana Just seeing your post so I thought I would weigh in.
Taurine is essential as you well know and heat processing destroys some of the naturally existing taurine. According to one article
"that it breaks down when heated, so cooking the meat will destroy over half of the available Taurine. "
You really can't use too much. I use taurine in my home-made food and still supplement extra with the feedings, since I have never been able to find if freezing can destroy any % of taurine. Since taurine is water soluble it is flushed from the system, much in the same way as B12 is. From the same article and others I have read:
"If you do feed your cat a homemade diet, you must add a Taurine supplement. Fortunately, there are few side effects of too much Taurine in the diet because
a cat's body can't store it. So if you make sure, however you do so, that your cat gets from one hundred to three hundred milligrams of Taurine per day your cat should do well."
http://petcaretips.net/cat_taurine.html
I personally use the NOW brand taurine. At one time it was one of the few taurine products where ingredients were not sourced from China. Not sure if that is still the case now, but I try to avoid supplements from China. You can buy it either in capsules in doses of 500 or 1000 mg per capsule ( gelatin capsule which can easily be opened) or in powder form and you measure the appropriate dose you need. Neither of my kitties ever noticed when I sprinkled taurine on their food.
It is available in the UK as well as other brands.
https://www.amazon.co.uk/s/?ie=UTF8&keywords=1000mg taurine&tag=googhydr-21&index=aps&hvadid=185250384879&hvpos=1t2&hvnetw=g&hvrand=10596124816250652361&hvpone=&hvptwo=&hvqmt=b&hvdev=c&hvdvcmdl=&hvlocint=9041128&hvlocphy=9001207&hvtargid=kwd-16619542167&ref=pd_sl_21ry5ioxc5_b