Problem was relating to the database, more specifically the Search_word_match table (ie the table the lists the location of all the searched words.)
It had blown out to over half a gig in size and was being belted by bots. We almost cooked a piece of ram in the server Im told

So, for this week I have disabled the search function (well, it'll still search, but yeild no results) and I'll check back in with the host next Monday
to confirm its resolved the overload. Then I'll turn the search back on, but I'll have to rebuild the search index manually. I need to exclude all
common words like 'and' 'to' 'the' etc to reduce the size of the table, therefore reducing the query load on the table, therefore not cooking ram.
I also have to put more antispam stuff on the signup page, while bots can't get through at the moment because I manually approve every single new account,
they are piling up dead at the front door. For every genuine new user account, there are 1-200 spam accounts created... A list I have to wade through every day.