Who to vote for?

Snapshot of my ward, from www.ukpollingreport.co.ukIt's that time again. A UK general election in around five weeks. And I genuinely don't have a clue who to vote for. Or, rather, I have reasons for voting for three of the candidates and don't know how to assess those reasons.

According to this handy website I have a minimum of five candidates to choose from, who are (in alphabetical order of surname):
Janet Ellard (Liberal Democrats) - my default voting preference is Liberal Democrat (someone has to, and cousin Nick expects it). But there is no chance of the Lib Dems taking our seat. I am very disappointed by the total lack of online data about Ms Ellard. The site I used has not yet got anything like a webpage, Twitter, etc. And the only link they (or Google) do have is to a LibDems page that currently isn't working. No literature through the door or visits. Poor show, guys.James Faulkner (UKIP) - not a chance in hell of getting my vote, I'm afraid. We have email and Twitter. No literature through the door or visits.Justin Tomlinson (Conservative) - I am not a natural Tory voter. However, Mr Tomlinson, the sitting MP, has proved an effective constituency MP, which makes me teeter towards supporting him as an individual, despite significant concerns about his party's policies. He is also a real local, rather than someone dropped in from on high. He didn't reply awfully well to my email about better funding for science. But at least he did respond, very quickly. Every kind of way to contact him, and he has called personally, and put literature through.Mark Dempsey (Labour) - my other voting choice, though the problem here is that I am more New Labour than the current version. My opinion of Mr Milliband has gone up a bit since the TV appearance, and I probably agree with more labour policies than Tory. Mr Dempsey is a local, rather than a parachute in. Good online access. He hasn't called in person, but I had a letter (rather bizarrely addressed to me and one of my daughters).Poppy Hebden-Leeder (Green) - very unlikely to get my vote. I've studied their policies at some length and they are bizarre on defence, spin fantasy on finance and are  very poor on science, particularly nuclear power. While I have a natural aversion to anyone with a double barrelled name, Ms Hebden-Leeder is local. Good online connections, though the fact that her Twitter name is @veggiepoppy does her no favours. No literature through the door or visits.So there we have it. UKIP and Greens won't get my vote. My natural choice, the Lib Dems, can't win and so far the candidate is totally anonymous. While I was quite fond of New Labour, the current Labour is veering back to the left a little far for me, which is worrying, and more worrying still, faces the dreaded cold hand of the SNP. While I haven't voted Tory before, the sitting MP seems to have done quite a good job, but can I put constituency effectiveness above party policies and their impact on the country?
I will listen to the TV debate later this week with interest, but I suspect this is the first election in a long time when I will be going to the polls and not know which way I am going to vote until the pencil is poised over the voting slip. 
All advice welcome, as long as it is a reasoned argument, not knee-jerk nonsense.