I was recommended the “map fat and calorie counter” by Roche book which gives most food in 100g weight and how many carbs per 100g. Freephone support line 0800 731 7138 you may get some help there @Rohan.
Obviously, reading the backs of packets/tins etc is useful too. Working out ratios needs a bit more of a controlled habit like @Mike says you may need to compare the same meal over a few days without different ratios but generally its not to bad to achieve.
It is disgraceful though that the level of diabetes care differs all over the country. I’m lucky I live in one of the best areas.