Hi homeseller
This is your current position
What price do you intend to pay for your new home?
How much would it cost to move and do it up?
The semi-d vs. detached is a very odd way of looking at it. If you had just said "We want to trade up to a bigger house or a house which is in a more convenient area" then it would be much more understandable.
But apart from trading up, is there anything "wrong" with your current house? Is it big enough? Do you get on well with you neighbours? Is it close enough to schools and work?
If you were living in a two bed apartment with 4 children and drug dealers on the street, there would be nothing to discuss here.
But if you are living close to schools in a 4 bed semi-d house with decent neighbours, you really need to discuss why you would want to trade up.
Brendan