PWP
The answer is yes you can convert a TMG/SLMG rating into pplA. You may get your hours credited you may not. The number of hours you get credited may not be as many as you would like. If as you say have caught the flying bug then fly what ever you can.
You say your dad will only let you fly 1 hour a month and that this is not practical. In what way is this not practical? It might not be the most cost effective way to go but if he's paying why are you complaining. 1 hour a month will take you longer than flying more often but it's still flying.