Extension over garage plus loft conversion

[TNJ]

I have just bought a new house in Kent (greater London). 3 bed semi with attached garage to the side.

I would like to add an extension over the garage to provide an extra bedroom/enlarged family bathroom on the first floor and also then do a loft conversion (probably hip to gable) so extending over the garage extension. I would expect the loft conversion to be sufficiently large to get two good size double bedrooms and a bathroom in. A number of properties on the road have had this done in the past so hopefully planning permission will be obtainable.

I fully expect that the garage foundations/walls will need strengthening.

I will get some proper quotes but was wondering if anyone has done a similar extension and would share how much it cost (excluding fitxtures and fittings such as bathrooms)? I appreciate that this is a bit of a "how long is a piece of string" question but would like to get at least a feel for the budget required - £80k? 100k? 150k?

I do not want to waste a builder's time by getting them round to quote and finding that I am being totally unrealistic. I did a loft conversion on my previous house (dormer) which came in at £40k including shower room, so I am reasonably comfortable I know the cost for that part on a standalone basis, but no idea when coupled with the over garage extension. I also know I will have to spend on other things such as a Megaflow system etc etc.

Thanks in advance.

[TNJ]

Thanks for the responses - it seems viable at around the £100k figure subject to the usual overspend on bathrooms etc!