Park by the white house:
http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&geocode=&q=CF48+4DR&sll=51.474113,-3.227148&sspn=0.026463,0.109863&ie=UTF8&hq=&hnear=Merthyr+Tydfil,+Mid+Glamorgan+CF48+4DR,+United+Kingdom&ll=51.50713,-3.721383&spn=0.000826,0.003433&t=k&z=19
Park at position "A" then walk through the style at "B" and then through the gate at "C".