I suspect you may not be in the North American market where V70s
were first sold as 1998 models (although they were sold in April
of 97 here). I think they were sold in europe as 1997s. But, the
headlight bulbs and glass may vary slightly from country to country
to meet local regulations. If you do find an online source make sure
it has the parts for your market.

As a general resource www.google.com is a good start. You can search
on "Volvo parts" and will find lots of sources. You could also
try "volvo parts uk" to narrow it down to something like the UK.

If you are just looking for headlight bulbs then you can search on the
bulb type listed in the manual -- lots of sources for bulbs; fewer for
replacement headlight glass assemblies (which are often cracked -- I
just noticed my own turn signal housing is cracked from a rock).