Hi Helena,
You're most welcome!
Sadly, as far as Im aware, Penallta is an abandoned site. I Believe the surface features are still in place, which can be viewed at a distance, however, the structures may be quite unstable and it would be safest to keep slightly away from them. (This is my Health and Safety Head on, wont mention it again!)
Some great information reference the colliery can be found at:
http://www.welshcoalmines.co.uk/GlamEast/Penallta.htm http://www.museumwales.ac.uk/en/bigpit/ )
The mining museum has a very great deal of artifacts and information, and even has a working head, where you travel underground, and with your guide view the working levels of the mine in complete safety.
If you have younger people with you, who perhaps dont want to go down the shaft, then there is also an above ground recreation of the workings. It is 100% worth a visit, and will really help you get a feel of what is underground at Penallta.
There are many ex miners around who are willing to share information, you may even find someone who worked at Penallta if you visit Big Pit!
All the Best
Matty
'FOR SALE: 1 Kidney and Half a Lung. If the Traffic Warden comes back to my car again, I can get more bits...'
'Instead of Helping, you stand, watch, and criticise, what a great British Achievement!'