TBH , there is still some information that’s unknown, is your current service underground or overhead, if underground and the cable isn’t going to enter inside immediately it appears from underground then some cable on wall (visible) is unavoidable, and if the entry point is on the first floor or second floor (for example) then it can be visually unappealing…overhead service can on occasion be taken inside at the higher floor level , but it’s more common to run down a wall to a low level and an external block (CSP) fitted and a second cable ran up the wall if the ONT is required upstairs, however there are examples of internal CSPs fitted , with the external overhead cable entering at a higher floor level avoiding most of the visible cabling …but as stated , this can’t be predicted, to a large extent it’s the engineer on the day that has the final say , but as a rule of thumb, it has to be safe (no unnecessary work on a ladder ) and won’t take ‘forever’ to accomplish , like excessive internal cable runs .
As stated , if you know that your requirements are likely to be unacceptable to the installer and what can be offered won’t be acceptable to you ….don't order.
FYI , there are different levels of installation offered to ISP’s from Openreach , but as most ISP offer the consumer a free installation that’s the shortest duration option one , if you are prepared to pay your ISP something towards the installation cost (so you ask for an advanced installation and they order that from OR ) the increased amount of time that can be spent , with a commensurate increase in allowed cable runs lengths etc may work as some of the time constraints are removed
