Upgrading broadband - need two HH5s - can it be do...

Question

Hello,
we have just ordered an upgrade to fast broadband (engineer to arrive Tuesday afternoon), but I think we should cancel the upgrade because of the odd set-up we have.
The telephone/network set-up is unusual, and somewhat less than ideal, for historical reasons, as ever.  The telephone line comes into the house on the first floor, with the master socket in the main bedroom.  However, the main computer, for several years the only computer, is in an outbuilding near to the house, along with my hi-fi and much else.  Please note that the buildings are all of stone with walls a minimum of a foot thick. So, we have an approximately 30' long extension cable (not the cheap kit cable) running from the rear of the master socket out through the eaves and across to the outbuilding, where the home hub is. A couple of years ago, wanting to use laptops in the house, and with the home hub on a window-sill facing the house, I installed an Edimax Wi-Fi range extender on a widow-sill in the house (facing the outbuilding), thus providing network access through the ground floor of the house. So we have the telephone line into the house, out to the outbuilding, into the home hub which gives a network there and over to the extender in the home giving wifi in the house. Yes I know it's a bit silly but we are where we are. I also replaced the HH2 with a HH5 bought off e-bay last year to give me gigabit ethernet ports to support my new NAS drive which supports a music network, amonst other things.
The problem is that I would think that the BT engineer (OpenReach?) will almost certainly only install the new HH5 in the house, and will not want to connect up to the long extension; indeed he will probably just want to disconnect that.  As I now have two HH5s I have been think of making the old one (in the outbuilding) a slave/access-point connected via ethernet cable to the new one in the house. Unfortunately I think it would be impossible to expect the installer to provide an ethernet cable connection to the outbuilding even if I offer to pay extra.  This would leave the desktop computer (my main computer), the NAS and the hi-fi off the network.
Can anyone say what you can ask the installers to do, and if they would just be prepared to connect us up to fast broadband using the set-up described above, so that we have faster broadband even if not as good as it could be? I should say that I would not be able to install cables through stone walls and between buildings myself, and I do not know where to fine a 'home' installer around here (Herefordshire, between Hereford and Ross-on-Wye).
I am about to try and cancel the upgrade and return the new HH5, but would be very grateful to hear if anyone thinks this is my only option.

Answer 1

Thank you licquorice and georgemac for your quick and useful replies; they are much appreciated.
liquorice, I think I will now wait, and talk to the installer when he arrives and see if he will leave the set-up as it is at present, but just upgraded; thanks, as I feel a bit easier about this.
georgemac, thank you for saying much the same, I guess he will just take the new HH5 out of its box (it's still in the hall of the house), and use it on the master-socket for testing.  As for the powerline adapters for, I presume, an ethernet connection from house to outbuilding or vice-versa (the latter would be using them on the the current set-up), I have thought of that but the power supply to the outbuilding comes off a 'spur' from the consumer unit in the house, and feeds into another consumer unit in the outbuilding.  Thus I am concerned that there may be too many circuit-breakers in the connection, which I understand may cause some unreliabilty. Trust me, I would like to re-engineer the whole set-up, but that would be a big task, and we may move in a year or two, so....
Thank you both again, I will try to see if I can just upgrade the system as it is, and if not I guess I will decline the upgrade. Oh, one thing, I currently have a micro-filter and phone hanging off the telephone socket at the end of the outbuilding extension (along with the HH5 of course). That link you provided georgemac, is saying that the extension will become part of the broadband circuit so I guess I must lose my landline phone in the outbuilding. I wonder how I get out of that... ho-hum.
Thanks again to both of you.