Sod, I have done 2 in recent years, neither of which (Dad and MiL) were much more complex than a house and contents, bank accounts, utility accounts etc. One had a will the other not. House value? Look at recent sales nearby, and adjust for the standards in your Dad's vs the ones for sale. Unless he had an estate, I would not be paying a valuer. Probate is not really interested in second hand sofas and fridges. Ignore them. The watch? If it's Phillipe Patik (sp) list it's value, otherwise, addit to a small total value for contents. Be sensible. Read all the OFFICIAL guidance online, fill in the forms, and away to go. It's worth setting up an executors' bank account, and when Dad's are all closed, you'll have a destination acc for them. Most big banks have a bereavement section, usually staffed with excelent people. DWP have a one call system for closing benefit accs. The registrar should alert you to that. Unless a complex estate, you DO NOT need a solicitor.
My condolences.
CG