I think this is the right place for this thread, and if not I am very sorry!

I have been looking at purchasing a Hornby Grange Locomotive for a couple of years and currently Hatton’s have one listed at £65 which I think is excellent value in the current economic climate. I know that the Alan Gibson range produces a RTR Grange Conversion wheel set which would require the addition of Bogie and Tender wheels and would cost just under £30 for a complete set of P4 wheels (again I think that this is a very reasonable price).
Has anyone converted a Hornby Grange and if so are there any major difficulties with a P4 conversion. I know from a friend at DRAG that the Bachmann 45xx and 4575 locomotives require a lot of 'packing' due to the narrow chassis of the model, however a 57xx was a simple drop and go conversion.
I imagine that the chassis for the tender will require work, as these are rigid so is there a suitable kit chassis with provision for suspension?
I hope that this thread makes some sense and any advice would be greatly appreciated.
Many thanks in advance,
Nick