Steve,
Nothing against you but, I can't understand why people keep asking for advice on pricing, it's your business, you decide on the price you want from the job, some people will price it very cheap, others will price it outrageously high.
If you ask enough people I'm sure you'll get prices ranging from under £300 to over £3000, therefore what does it achieve? Nothing.
Be confident in your own pricing structure, I'm sure you've cleaned all of these individually in the past and know how to price them up, therefore just multiply it up for the volume here and if you think it necessary offer a job lot discount if it can all be done together.