That evidence should ideally be spread over 24 months, means a letter/document at around 4 month intervals.
The Home Office want to verify that you have been co-habiting as a couple over that period.

Try to think about something along these lines:-

Driving License
TV License
Electricity Bills
Gas Bills
Water Bills
Council Tax Letters/Bills
Bank/Building society statements
Bank letters
Marriage Certificate
Registry Office Letters
NHS medical cards
Letters from GP
Sports club membership cards
Insurance Quotes
Letters from Church/Religious Organisations
National Insurance appointment letters
HMRC letters
Personal letters from friends/family etc
Mobile phone bills/letters
Tenancy agreements
Insurance policies/certificates or other correspondence
Loan agreements
AA,RAC or similar membership
Letters or other documents from your GP, a hospital or other local health service about medical treatment
Letter confirming registration with a dentist, etc – providing these documents show your home address and the date first registered

If you're really having problems you'll need to provide some reasonable explanation as to why and try to provide letters of support from other people such as family members or more especially from those folks who are able to say countersign passport photos etc
such as:-

- Accountant
- Airline pilot
- Articled clerk of a limited company
- Assurance agent of recognised company
- Bank/Building Society official
- Barrister
- Chairman/Director of limited company
- Chiropodist
- Commissioner of Oaths
- Councillor (local or county)
- Civil servant (permanent)
- Dentist
- Director/Manager of a VAT-registered charity
- Director/Manager/HR Officer of a VAT-registered company
- Engineer (with professional qualifications)
- Financial services intermediary (eg a stockbroker or insurance broker)
- Fire Service official
- Funeral director
- Insurance agent (full time) of a recognised company
- Journalist
- Justice of the Peace
- Legal secretary (fellow or associate member of the Institute of Legal Secretaries and PAs)
- Licensee of public house
- Local government officer
- Member, associate or fellow of a professional body
- Member of Parliament
- Merchant Navy officer
- Minister of a recognised religion (including Christian Science)
- Nurse (RGN and RMN)
- Officer of the armed services (active or retired)
- Optician
- Paralegal (certified paralegal, qualified paralegal or associate member of the Institute of Paralegals)
- Person with honours (an OBE or MBE, for example)
- Pharmacist
- Photographer (professional)
- Police officer
- Post Office official
- President/Secretary of a recognised organisation
- Salvation Army officer
- social worker
- solicitor
- surveyor
- Teacher, Lecturer
- Trade Union Officer
- Travel agent (qualified)
- Valuer or Auctioneer (fellows and associate members of the incorporated society)
- Warrant Officers and Chief Petty Officers


Try not to get too hung up on documents/letters with both your names. Although that's the simplest it's often not the easiest.
As I said, the requirement from UKBA is principally to demonstrate that you have been living together at the same address(es) (and still do) throughout the 2 years probationary period.

Try to have your wifes name on as many 'ID' documents as you can. It's always useful.

I've never known a refusal for lack of named letters etc

Hope it helps a little.