You don't need a DBS to act as agent. You just sign a declaration.
Legally speaking you don't need to appoint an agent, if you fail to do so, you are your own agent. So Aimee technically didn't need to name David.
Where this might get really murky is on this clause on who is disqualified from standing for local election:
You have been sentenced to a term of imprisonment of three months or more (including a suspended sentence), without the option of a fine, during the five years before polling day.
Source: www.electoralcommission.org.uk/__data/assets/pdf_file/0007/141784/Part-1-Can-you-stand-for-election-LGEW.pdf
Check out the archive links for these:
www.thefreelibrary.com/In+the+courts-a0357547534
CASES heard at Coventry Magistrates Court on Thursday, December 12, included: David Challenor, 45, of Charterhouse Road, Lower Stoke, was found guilty of failing to provide suitable environments for two corn snakes, a bearded dragon, two cats, three dogs, a hamster, two hedgehogs and two rabbits. He was jailed for 12 weeks, suspended for 12 months, with 200 hours' unpaid work, and told to pay an PS80 victim surcharge and PS500 costs.
Coventry Telegraph 4 Feb 2014
www.thefreelibrary.com/In+the+courts.-a0358278849
CASES heard at Coventry Magistrates Court on Friday. December 20, included: Tina Challenor, of X address, was found guilty of failing to provide suitable environments for a corn snake, a bearded dragon, two cats, three dogs, a hamster, two pigmy hedgehogs and two rabbits. She was jailed for 12 weeks, suspended for 12 months.
Coventry Telegraph 11 Feb 2014.
Is this a problem? Seems they might just have dodged being disqualified by a matter of days.
Further to this, in order to stand at election you need to be nominated by a number of people in your constituency. They don't need to be party members, just anyone who lives in the relevant constituency. You need ten people to support your nomination (family members are allowed I believe). I'm not 100% sure what the legal duties/responsibilities of those nominees are - I think it is just to confirm they have enough support in the constituency rather than be 'character witnesses'. Generally speaking, I think the perference is to use party members to give credibility to the nomination, but this is only convention rather than legal requirement.
The responsibility of eligibility, I believe lies with candidate and the election agent alone in law. I can't see anything which pins a legal responsibility on a party, oddly enough. I think there is a reasonable argument to say there should be.