From my experience, many local caterers in Amersham can indeed accommodate same-day requests, especially for smaller functions. I remember a last-minute gathering we had, and the caterer managed to pull together a delightful spread within a few hours. They tend to have a selection of ready-to-go menu items and can quickly adapt to short notice. In exploring this further, I found this site which might be helpful for you too. Before I forget, it's always best to call ahead and discuss your needs as soon as possible. Flexibility is key, but ensure you provide all necessary details upfront to make their job easier. With the right caterer, you can still have a fantastic event even with minimal planning time.