A bigger house is always worth more than a small one with bits tacked on.
Verify the Planning Permission and Building Regulations approvals with great care. A non-compliany conversion adds negative value to a house because you have to factor in the cost and disruption of ripping it all out before you do it again properly.
The conservatory is part of the house and is open plan to the kitchen/dining area. I would have preferred a garden room tbh but the conservatory is quite nice and in keeping with the rest of the house. In the long term I might look to replace with a garden room.
Without the loft conversion, the original master bedroom (which is elsewhere in the house) is quite small so wouldn't fit a dressing table for example - which is a must for me. So the revised layout means you have a large master with a separate dressing area for dressing table and chest of drawers etc and then access to the en-suite. The only issue I have with the loft conversion is that there is only one window which isn't enough IMO. I would want to add an additional window in the long term.
Is the conservatory done well? Is it like a part of the house, or a cold shut-off storage area? I think it is hard to say without knowing the area / market / housing stock. At the end of the day the value is however much someone is willing to pay for it. A bigger bedroom wouldn't add too much value for me, a dressing room would be wasted on me as well. If the conservatory adds extra living space that you can actually use, that would add quite a bit for me. Some people hate them though and would consider them a problem with the house rather than an asset. <unhelpful>
Seen a really nice house that has had a conservatory added and a loft converted to form a bigger master bedroom. Hasn't added an additional bedroom to the property though as a smaller bedroom has been cut through to provide access (the smaller bedroom is now a dressing room).
If the value of the house without these works is c £450k, how much do you think these extensions would add to the value?