Chris, I think you're coming in at a time where the LEGO reselling party is coming to an end. I'm not saying there is no more money to be made; what I'm saying is that the ship is full and the general consensus is that people joining now are going to have a hard time turning this into something truly profitable. Many here are getting more close-lipped on their strategies, as there is now a lot of competition. Plus, the general state of the LEGO market is post-euphoric, with too many sets out, too many people buying for reselling/investment, a reduction in buyers and big discounts around that were unheard of even 1 year ago. Combine that with an influx of new forum members over the last 1-2 years, with many coming with the expectation that they'll be handed their fortune on a golden platter, and you can understand why there is a lot of sarcasm around.
This has nothing to do with you as a person. There will always be some headshaking when people hear about you plonking down 2k GBP in less than 8 weeks, but you own your own decisions. Read into the comments what you want, but see through the sarcasm and understand that some people use it to express concern about your strategy. Nobody here would chase you away - but many (myself included) will post about the victories and the extremes, not about the daily grind of investing/reselling LEGO. You might want to consider such a posting strategy yourself as well.
There is a ton of info around on this forum, and lots of comradery and compassion. Take your time to get familiar with what is appreciated (deals! success stories! fruitcakes! delivery failures! set news!) and you will find that this forum will become a second home.
And yes, everyone posts something sometimes that gets a negative response from others (epic deals in Target, anyone?). Just read it as it is intended: an opinion on what you posted, and use it to shape what you post and how you post it in the future.
We all started with 0 posts and 0 reputation, and we have all posted stuff that others didn't like. You'll be fine