While i don't know about your coin specifically (i live in canada) we have had a metallurgical change to our coins recently.
Provided your coin hasn't changed weight or size, it should go through the acceptor just the same.
The different metal means the magnet in the square portion of the acceptor is grabbing the coin and stopping it (thinking it's a slug)
remove the screw and discard the magnet and the metal retainer and screw.
your coins should feed fine then. if they still don't i would suspect your coin has changed weight and you will need a simplee size comparator like a "imonex" brand such as the v9 series. not sure if you can get a 10p size from them. but it's the sytle you would need.
it simply separates coins by diameter making it accept all manner of coin regardless of weight or metal content (also washers and slugs of the same diameter as well though.)
http://www.imonex.com/Category_Amusements/v9_series.aspx