From the Electoral Commission's list of electoral offences (note, it's a PDF):
"A person is guilty of treating if either before, during or after an election they directly or indirectly give or provide any food, drink, entertainment or provision to corruptly influence any voter to vote or refrain from voting. Treating requires a corrupt intent - it does not apply to ordinary hospitality."
The photography in the polling station issue might come under "breaches of the secrecy of the ballot", but that's probably a bit trickier and not the key issue since it's up to an individual whether or not they tell people who they voted for.