Removal of chimney breast in London Victorian terrace

Hi Rated People Experts!, Regarding a Victorian (1890) 2 story mid-terrace house in South East London (Lewisham). It has chimney breasts in both the front and rear rooms on both levels. Am considering removing the chimneys on both levels in the rear aspect (which is the kitchen and 2nd bedroom). Having conducted lots of (internet) research I have confirmed the following... 1) Begin party wall proceeding with affected adjoining Neighbour, of which I intend to serve myself using the Government guidance/example letters in a document entitled "Party Wall etc. Act 1996" "Explanatory Booklet" "June, 2013 Department for Communities and Local Government" 2) Engage the local councils Building Control to confirm process, obtain permission and whether gallows brackets or steel beam is preferred (Councils appear to have different approved solutions). 3) Engage services of a structural engineer to calculate the steel required. Can the experts provide me input on whether I have covered all the pre-work (other than engaging a builder to do the work/obtaining a skip etc..). Do you have any *very* approximate numbers I should be looking at? Thanks in advance,