That doesn't mean lawyer up or shut down at the first request. Of course you should be prepared, by doing sensible things like having an up to date privacy policy, and only keep the data that you need and that you have permission for. However when it comes to compliance, if you get a request, be sensible. The time to lawyer up is if you get a notice from the ICO, if you think it's unreasonable and/or you don't think you can comply with it. I've dealt with the ICO quite a bit, as I've appealed a few FOI requests, and they've always been very reasonable, if a little overworked and slow to respond.