Language script for applications and web pages that do not define it

When I access Natwest online banking or Motor websites that display monetary amounts The symbol shown is in Thai script and is the sign for Baht, local currency. I am using Win XP pro and IE6. My computer is set up for Engish UK and English US with the pound sign as default for currency.
If I access tools menu, internet options in IE6 and general tab, then fonts, I see 'Thai' displayed in the language script box, which would seem to be the problem. However when I change this to Latin Based or User defined and click OK, the window panel closes as if accepting the change. But when I open it again it has reverted to Thai.
I have found that all other computers I have seen so far, 3 Thai and 1 English whose default is Latin Based, are also unable to change that Language script option, only the actual font. How can I change the default without re-installing XP, surely there must be a registry setting for it?
The £ key on my keyboard works fine in Microsoft applications such as word, but on these websites and in Actinic Catalogue, the same key gives a thai baht symbol. Although I am based in Thailand, I don't need to use their script, but would prefer to be able to it if the need arises.

 

I looked around some (internet searches and regedit) and can't seem to find anything exactly on point.

What happens when you go to a problem page and then view~encoding and force the selection you want?

 

Newt, thanks for your interest. I would like to try that but I don't know how to do it.

 

Thanks, problem sorted now.
This is something that is set by XP at time of installation and (apparently) cannot be changed after, even though there is a drop down box in IE6 that looks like you can change it. The Thai bonehead who sold me the PC and set it up, set it to Thailand as the 1st region asked for, even though I do definitely not look thai and my Thai is limited to say the least. The only solution is a clean installation, which I have done, bye bye programs, bye bye documents etc. Of course I have back-ups so no great problem, just time and frustration.
For interest, go into IE6, Internet options, General, Fonts.
Try to change the Language script (which is now Latin based, usually) and OK it. There you are you see, you can't can you, so why have the box? Microsoft knows!
But after re-installation, where that previously stubbornly said Thai, it now says Latin Based and all is well.