Karen- take a deep breath and plunge right in!
Clubs are brilliant- you have an interest in running, they have an interest in running, it's a perfect mix!
I'm also moderately confident that whilst you describe them all as "very, very fit" odds are that as in life you also probably just scoped out those who looked the fastest ignoring one or two of the less fit looking individuals! Whenever I'm at a race I always single those out that are going to be exceptionally quick and odds are, that normally, although there's always a few surprises they'll finish in the top 20. There are probably soe there at the same level as you.
They're friendly, will love to talk to you about your running and how to get better ( try finding the club guru, there's always one!) and about their own I'm sure and it'll get you really connecting with people.
Obviously some are worse than others and some are better, but it sounds like you've found a good one! Keep up your own work and quite soon you'll be right with them. To run a 35 minute 10k after only two months is brilliant, I'm quite confident that you'll be well under 30 within a few more months (clearly some natural talent there!) and this way you'll be able to measure your progress week to week compared to how you do against the others.
The only problem could be if there normal run is longer than 5k, but if so, look for little "shortcuts" on the route to get you back, and from the sounds of it, you're going to be covering all the distance you need to in no time.
Best of luck,
Bryn
p.s. THe clubs that I would warn some people ( particularly with a fairly high number of beginners here) are "athletic clubs" whilst the people are often just as nice and quite a few have a large adult section the same as the running clubs, often they are also quite youth and track orientated, with few seniors, and basically much faster runners. In my training group at my AC (as opposed to my running club and jogging group), we've had senior sub 35 minute 10k runners come and join the group and they just struggled really badly to keep up on the shorter reps, and the younger group he'd have been too fast for and really too old to connect at all with. In the session we did tonight, the South of England silver medallist over 800m and inter-area champion ( beat best runners selected for South/Midlands/North) had to drop out as it was too tough for him.
Still look into ACs but check it has an adult road running section, running clubs are normally fine.