sound problems with Panasonic sc-BTT590 (1 Viewer)

I have a 9 year old Pioneer 43 inch Plasma which has a seperate media box. 2 weeks ago I had to replace my home theatre set up and bought a Panasonic SC-BTT290 system. Because of my older TV the only connections available to me are the HDMI leads. Everything works perfectly, EXCEPT, whenever I turn the TV back on, I have the picture as you would expect but no sound. The only way to achieve this is to go to the Panasonic remote, choose home menu and select HDMI 1 and we then have sound. OK, can get there a bit painful and not popular with my wife. I have spoken to Panasonic technical UK who have confirmed I have right leads in right places but suggest that because my TV does not incorporate arc, I am stuck with the problem and I should buy another TV! Does anyone have any suggestions, please, please help. Thanks Steve

It would help to have a little more info, specifically, what signals are going where (e.g., Do you have an antenna and/or cable, to what device is it connected. Elaborate a bit on the media box, what is that providing?)
But I'll take a shot without that. As long as you don't have an over-the-air antenna connected directly to the TV, the lack of ARC is not the problem. I think the issue is you have to turn on audio passthrough for each device you have connected to the Panasonic. Look on page 23 of the manual (looks like this, with a table following):
EXT IN
When you want to output audio of an external
device from this unit, select the name of the
terminal to which you have connected the device.

He means one of these...
http://www.ebay.com/itm/Pioneer-Elite-PRO-R04U-Plasma-TV-Media-Receiver-Tuner-HD-NR-PRO-1120HD-PRO-1110-/330842464142?pt=Receivers_Tuners&hash=item4d07bf5f8e
It would help to know what your other sources are. As I suspect the problem is your integration is backwards or this HTiB simply doesn't have enough inputs.

Looking at the HTiB, it has two HDMI inputs and 1 digital input. Your "media receiver" should not be receiving your sources. The HTiB should, and that would eliminate your problem...I think, cause we have no clue what your "other" sources are.

Thanks for your help. The set up is as follows: Pioneer media receiver PDPRO5FE which is 8 years old has 3 scart connections and 1 HDMI connection. As new equipment does not have scart these are obsolete so HDMI TO Panasonic home theatre HDMI out arc av out then have HDMI1 from Panasonic to Amstrad DRX 890 sky box. Hope that makes sense. Can't see how I could change any of these.

Forget ARC...cause it doesn't matter.
Your explanation doesn't help much, cause you are using too much verbage....
Plainly, here is what "should be" going on...
Amstrad Sky Box HDMI into HTiB. Pick either one, makes no difference.
HTiB to "media box" via HDMI.
There should be only two wires...both HDMI.
I have a feeling the audio problem is that you have the audio set from the HTiB defaulted to "go to the TV", hence why you don't have sound till you "push a button". The audio(in EVERYTHING HTiB/AVR) can only go "out" one place at a time...the TV or the system. I'm going to fathom a guess that Pioneer doesn't have speakers(cause here in the US we didn't get that media receiver, and it was an "option" here to get speakers with the display, assume it was that way there...and not very many people bought the speakers).