That is a great time, let alone for a first ultra... I'd reconsider not doing any more after a performance like that...!!!

Haworth Hobble in march is a great race and lots of history, similar distance but a bit less total climb, you'd probably be looking at well under 6 hours (something I've not yet managed)...

I'd also recommend the Lakes Mountain 42 in April which is more of a fell race in nature, but very long. Very low key atmosphere and stunningly beautiful on the first section and over Helvellyn. Tough race though. 42 miles and something like 10000ft of climbing.