Dont know if this is still relevant (whether you have completed your travel or not) but I went on the Beach & Bush tour last year & absolutely loved it.
It was when I got there that I remembered about all the bugs & snakes & spiders but there was really nothing to worry about - really the only spiders we saw were in the bush on Fraser Island (Huntsman - was HUGE but apparantly they are harmless) & then another 2 in the bush walking to Whitehaven Beach in the Whitsundays.
There were quite alot of bugs in the outback, mainly flying things but those pesky flies are so little & annoying. Walking around the Olgas we got so frustrated with batting them away that that afternoon a few of the girls in my group went & bought hats with mosquito nets for the next days tramp. They looked ridiculous but I have to say I think I would recommend one… I even ended up swallowing a fly! Eeeww!
But in terms of spiders, I dont think I saw any in the outback.
I also looked at accommodation reviews beforehand & was also a little worried as to what I was going to come across - most of our accommodation was really good, no complaints.
The only place I can think of that could’ve possibly had bugs was Fraser Island - but thats kinda unavoidable because the lodges are surrounded by bush. & most places have screen doors to prevent them coming inside anyway.
It was all 3 or 4 share depending on where you were staying, & also really close walking distance to town - once we arrived the bus was prettymuch parked up until we were ready to leave for the next destination.
Ok so I just read your question & see you are asking about the pre tour accommodation - Is that at WakeUp Hostel? I didnt actually stay there beforehand, I stayed at YHA The Rocks (because it had an awesome view of both the Sydney Harbour Bridge & the Opera House) & I just got a taxi to WakeUp on the departure morning. If you are still worried then I would totally recommend this hostel, it was pretty nice & clean & secure with good facilities.
So even if this isnt relevant to you, hopefully it will be helpful to someone else
& if anyone else hasn’t booked yet, I would totally recommend doing the full Grand Ozzie if you can - I finished my tour after 19 days & totally regretted not going all the way to Darwin with a couple of others who were continuing on.