Place gelatine strips in medium-size bowl, cover with cold water and soak for 5mins, then drain.
Blend strawberries with sugar and lemon juice, then pass through fine-mesh sieve into measuring jug (avoid pushing through too forcibly as don't want seeds to go through). Should have 600ml liquid; if not, make it up with water. Bring to boil, then take off heat and stir in gelatine until completely dissolved.
Divide jelly solution between 4 150ml ramekins or dishes, and leave to cool. Cover and chill overnight. Serve with whipped cream and sugar sprinkles.