Change in circumstances and sponsorship for visitors visa

[successatlast]

I was working for a company for last 2 years on work permit and changed to Tier 1 visa 5 months ago.I am getting married next month and need to invite my parents for marriage.I also resigned from my present job this month which I have been asked to reconsider.I have following queries
1) Do I need a employers letter confirming my job status to sponsor visa as I dont think it to be appriate to ask for one now??
2)I dont have payslips as I am Tier 1 and havent paid my tax yet as its been only 5 months so would my bank statements be adequte.
3) Do I need to pre book a ticket for UK visa
4) I rent flat so along with tenancy agreement do I need to attach council tax etc??

kindly help