I was exactly like you last year wewilson,my sons diet seemed to be getting more limited with each day and I was really starting to despair and decided it my aim for the year was to get him to eat some famil meals with xmas dinner as the goal.
I am certainly no expert and it has been a case of trial and error (like all parenting!)
Some things that have worked for us are we cut out all snacking in between meals for all of our children except one biscuit and a piece of fruit after school to tied them over.
we drew up a chart of lots of different foods that he had never tried and we made it a challange to find at least one new food a month that he would continue eating. we rewarded my son with little treats for every positive step he took towards achieving this with small treats i,e 5 mins extra time on his xbox etc. the more adventurous the more time.
So to start wth we agreed on some new foods he would try and at first it was touching a new food, helping cut / cook a new food, taking a sniff at the food , licking the food, trying a tiny little bite (even if it was spit out!) and scoring each food,i.e 1) he couldnt tolerate it, 2) it wasnt nice but he couldtolerate it 3) it was ok 4) he liked it and would have it again.
Obviously to start with everything was marked as 1 but he soon realised he he would have to go back to the beginning and try them all again until he found at least some that he would eat, and it slowly became easier he realised he was in control as he could choose in which order of the agreed food list he would try next if he didntlike it he could cross it off as long as he tried it and agreed that at least some werebettr than others.
Its been amazing how much he has progressed. thee are still alot of foods he wouldnt go anywhere near but sometimes he even asks to try new foods without prompting.
Last year his diet was limited chicken dippers, toast, cheese sandwiches
biscuits, chocolate, raisins, milk, apples, yogurt and ribena.
He now eats chicken, turkey, pork, gammon, sausages, ham, spaghetti (cooked no sauce) pizza, jacket potato, roast potatoes, ketchup, yogurt, cheese, apples, raisins, dried cranberries, strawberries, carrots, red peppers,cooked onion, things with tomatoe puree , lasagne, milk, milk shake, apple juice, any brand of blackcurrant or orange squash.
Sorry for such a long reply but hope it helps x