I managed to resolve this myself by trial and error. From the CSS file I deleted the reference to H1.
I then amended my main.html to read:
<div class="logo">
<font size="7"><strong>Altinkum Property For Sale</strong></font>
</div>

So I still have the same header but it is no longer H1, which means I have been able to set up individual H1's for each page.