The key issues will be:
1. Is it going to be a shorter run of pipe from the gas meter or longer? If longer it may require some or all of the existing gas pipe replacing with a larger diameter one.
2. Do you want it in a position where the flue would be too close to a window or other opening?
3. Can the condensate pipe be run into a drain, preferably internally?
4. Can you get a new flue, and possibly plume kit, for the make and model of boiler you have? (Its most unlikely the existing flue can be re-used).
5. How can the hot and cold and flow and return pipes be connected into the rest of the system? (Easy access to under floor, presence of solid / laminate flooring).
6. Are there any physical reasons why the desired new location is impossible? (No outside access, is it a bathroom etc.)
It's not really a question which can be answered remotely. If you have a heating engineer you trust (e.g. the one who does your annual service?) ask them to quote, or pay them to draw up a specification of what is to be done.
