Hi Rich
Don`t know if my UK experience reflects what goes on downunder but I`ll share it. I was in a similar boat in that I took early retirement from work and , having had similar experiences to you with some good competition results, requests to cover some events (paid) and finding that it might be possible to turn a hobby into something that paid for gear and the odd holiday I decided to give it a try. Mainly done events / couple of hotel shoots etc so far and tried to get more into weddings last year. I too offered myself to various local photographers whose style I liked and even got offered a paid assistant post at one time (he re-thought when he realised a studio he bought came with expectation to keep another 2nd shooter on). From most I did not even get a reply, same when appying for paid posts through local sites advertising photography jobs. I found that the only way I got initial experience was by joining dedicated Flickr wedding groups and getting on there , posting a bit and asking for assistant work through that. Still early days for me - just formally registered in last month but managed to get some second shooting experience and a handful of paid joint shooting jobs that at least give me a portfolio , along with a portfolio shoot I took part in which was amazing.
Here it is a heavily saturated market for weddings with prices driven down in my locality which makes me glad I am not dependent on it for a living. You need an excellent website with good google performance ( which I have not got yet) and networking is the key. You will find some local pros hesitant to use you for fear of competition but you`ll find others OK. You`ll need to sort out with photographers what you can / cant do with shots when shooting - some will give you cards to shoot with that you don`t get to edit / use yourself, others might let you have them, others will use you as hands / body for carrying and soe will let you use them with agreement of bride and groom. Some will have 2nd shooter contracts that state terms and exclude use of shots for portfolio so before giving your time for free decide what you want out of it and make sure you agree it with them. I was very disappointed with response levels to my offers of free help but told latere they are buried in such requests. You should turn up at the studios of bigger ones and ask to see them / make an appointment rather than just write and get a portfolio of portraits / reportage type stuff and posed. I remember my worst response was from a guy who said he was sick of being used as a job creation/ training scheme and asked me not to bother him again - only contacted him once! Funny thing was, registered with a national wedding photography organisation as he was, I next saw him named in a local press article that went viral throughout the world when his company were sued for some of the worst wedding shots I had ever seen. Think he could have done with a good 2nd shooter after all