Inexperienced parents + child's hobby = cheap as they can get (normally) for the simple reason parents know kids can go off hobby's very quickly, so they the parent is smart by not risking to much cash on it.
This may not be the case with you young man, well hopefully anyway, but that may help you understand the main reason why you parents feel £130 is to much on a boat...
I'm sure many here will tell you that £130 is a reasonable sum of cash for a reasonable boat (fast electric or scale model @ a beginners level) but the majority of us will also tell you that £130 won't buy you half a decent boat, just as an example my tug project, being a semi kit not everything is included so i have to spend more to finish it, kit cost £300 .... + extra parts to finish £250 + the electronics (Action of course) £120
Total... £650
My daughters Seaport tug.... £39.99 to start, luckily i had spare electronic parts, but still there was another £40 there spent one way or the other, then paint £30, and a few other details... there was £120 roughly spent on a 5 year olds toy.
These example may help you to teach your parents that modeling is not a 'cheap' venture, (it can be done cheap but the majority of us will spend far more then £130 on a boat) and may aid your case in getting the extra cash.
Selling old toys and stuff is a great way to finance your project and actually will show your parents your commitment to modeling, which will in turn hopefully justifies to them that spending a bit more is worth while.
There are also other things you can or may do, say getting an allowance (do chores around the house, help your mom out with the dishes or washing) think your a bit young for a paper round at present but i overall you need to prove to your parents that your committed to the hobby for them to spend more on you.
All my hobbies i had to do off my own back, from the age of 12, i worked several paper rounds in my days, asked for cash for birthdays and xmas, all was saved to get me started, it taught me valuable life lessons in the process!
kids are fickle, parents are nieve and it all adds up to not getting what you really want until you start working! (unless your one of those rich brats that need a slap into reality

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