Rent in advance of more than 1 month will be illegal soon, and probably by the summer (Renters Rights Bill). This is as a result of the Gov trying to protect tenants. Sadly, the irony is that this will not help you, as this option is taken off the table.
If you are unemployed, I suspect you’ll have little chance of finding a tenancy, even with a Guarantor service. Maybe you’ll need to look at short term (holiday) lets initially, whilst you sort the job, and get settled. These are more expensive though.
I live in Kent, I’m a pensioner with health problems and currently classed as homeless, although the council have put me in temporary accommodation to which I could get notification to leave at any time.
I am really struggling to find private rental, especially as I don’t have a guarantor, not being nasty but if I’m having no luck then I doubt you will, especially as finding somewhere close to the LHA rates is very hard.
Are you thinking of just a room? If so most of them (admittedly bills will probably be included) are priced as high as the LHA rate for a studio/1 bedroom flat.
What area of Kent? Do you know the LHA rates for each area in Kent, they vary greatly from about £392 per month to £458 per month and good luck finding one anywhere close to those prices.