Admiral, Bell & Elephant were the most competitive for me at your age (I was 22 when I bought mine) I was paying around 920ish i think with mods declared.
Now I'm with Chaucer & paying £950 with all mods covered like for like but they seem a bit hit & miss with some others who have tried them. Thats at 23 with 4NCB & been driving 5 years.