Spot silver is about £21.50 per Troy ounce, which is 31.1 grams, so that's pretty close to 70p per gram. Any bullion dealer offering you less than 55p is probably in breach of his licensing conditions.
No such thing as a bullion dealer's licence since the 60's- and then only briefly-anyone from 1971 onwards can buy as much or little silver and gold as they please including coins.
I'm getting 51p per gram for .925 which is the most common so Mazie is right anything around 50p is about right.