Feedback on adding maximum value

Hi All. I know this forum is for selfbuild house but I need some advice from you experienced people in terms of if the planning design is most appropriate most value for money option. The property is detached house with c 0.25 acre of plot and was previously used as a care home but it is currently used as 7bed HMO and has Sui Generis planning permission and HMO licence. Current value is based on income multiple based on  the number of rooms so theoretically number of rooms go up, the value also go up. Hence in that basis I am planning to increase the rooms from 7 to 11 or 12 (if possible). One option was to rebuild one bed flats units but I was not sure numbers of flats I would have achieved in there and the cost of entire rebuild meant that I went with additional rooms. I did some alterations/remodelling/refurbishment in 2019 and ended up spending c125k including finance costs. It included new plumbing/electrics small utility extension, hence I did not want do radical changes in remodelling option but I think if I can recoup that via further increase in the value from rebuild of flats I might treat that 125k as sunk cost with a heavy heart but that would mo doubt hurt. I attach the exisiting and proposed plan for remodel/extension option and would appreciate your feedback on it or if you think rebuild would be more suitable as flats then happy to consider that as well. Thanks.

Edited December 27, 20214 yr by Zak S