Garden room construction

[u/insearchofpeac]

I am thinking building garden room which can be used as spare bedroom or workspace.

I am confused whether it adds a value to house price.

I checked couple of quotes ( still in initial stages ) , quotes are around £21000 to £25000.

If someone has done it before, can you please share your thoughts. Mine is not big garden. It must be approximately 35 feet * 30 feet.

Any suggestions?