The ESL areas are RA1s for the most part - you can plan though them and expect a clearance. They are usually released above FL200 to the civil sectors anyway. Hornets can go that high, but you usually don't see them down at Sale. I think they did a simplification a few years ago so there wasn't a heap of vertically spliced areas that made NOTAM lists hard to read. So hence we have 'just in case' airspace - we will activate the lot as it's easier to read, and then release what we don't need and you can flight plan though them. Reasonable compromise I'd say.