As a landlord, I'm not impressed with 6 months rent up front - we've taken such tenants twice and both times after the 6 months they couldnt pay.
What a landlord wants is a reliable, long term tenant who can pay their monthly rent from their normal monthly outgoings. A guarantor is a huge bonus. This should be someone with a permanent job and preferably their own house.
You should offer to sign a 12 month contract, explain you want the property longer term, offer to meet the agent or landlord at your current house (to see its well maintained and that you're a decent person, your kids not hooligans etc), prove you're entitled to enough tax credits or whatever to pay the rent.
And dont be an awkward potential tenant - ask for a reduction in rent, ask for rooms to repainted, carpets to be replaced, to accept pets, add ovens etc all these things mean time and effort for a landlord and although not unreasonable you are trying to be the perfect tenant!
I (try to) choose tenants that are honest, decent people - not because they have a secure well paid job.