If you are two years away, I wouldn’t worry about getting a valuation or a mortgage in principle yet - it’ll be very outdated.
Right now it’d be about doing any work that needs doing - if you get another two years out of the bathroom, will it look in desperate need of updating then? That will affect value - and saving.
You’ll either need 3 or 6 months payslips for your new mortgage, depending on the bank, but usually three. You’d be able to get an idea of how much they’d lend you on your new salary through getting an AIP, and then you’d do viewings, and when you have an offer accepted, convert your AiP into a full mortgage offer.
Decluttering is a good idea.
Estate agents fees and solicitors fees change a lot; most places near me charge around 2-3% of house value as the EA few. Solicitors will vary depending on what you’re selling; what you’re buying and where. Leasehold tends to cost more. Stamp duty will depend on what your purchase costs.
But the numbers really only make sense when you’re ready to go. We first listed in February 2020, came off the market last summer and are now in the process of buying and selling, and everything is different to last years figure. The valuations; the costs; etc.
So your big things right now are maintenance, decluttering and saving, realistically.