PhD Finance Help

[zeus'thunderbolt]

Hello everyone, my first post so here goes. 

I've been accepted onto a PhD programme here in the UK (hallelujah!) and I'll be starting at the beginning of October. I started out this topic simply thinking I would seek out some laptop advice, but it's transformed into something larger.

To cut to the chase, I've had bad experiences regarding computers throughout my bachelor's and master's programmes. My first MacBook Pro was a cheap-ish five year old purchase from the internet to start university with. It lasted about two years until one morning the harddrive decided to self-combust with no data back up. A quick trip to a retailer and I came home with a shiny new MacBook Pro (Mid-2012). This worked perfectly until last year, when the harddrive went on the fritz part way through my master's thesis. Before the breakdown, things were running quite slowly. The system itself has become slower and slower, but is still just about workable, as long as I don't demand anything of it that is too intensive. This, combined with my past experiences, has led me to a crossroads. Do I upgrade the RAM and buy an SSD for my current laptop, or should I fork out for a new one? I work for an Apple retailer at present, so I'm surrounded by the new 2017 MBPs almost every day. I've been thinking a 15" for a little while, due to the better processor and greater screen real estate. As a bonus, I get a fairly decent staff discount, which would put a 15" MBP at just under £2000. An upgrade obviously makes more sense financially, but I don't want to get a year into my PhD and have to buy a new laptop because my old one has finally given up. Speaking to a friend, he suggests that an upgrade would be fine for a little while, but obviously the machine itself will become too outdated anyway. The other option is to use my present laptop up until the last moment and buy a new one then. Buying a new laptop obviously doesn't guarantee maximum longevity, but I'd really like something that will last at least three years for my PhD, and then any post-doc work and beyond. What have fellow PhDers done? 

Now, here comes the more philosophical bent of the post... I'm in a fairly well paying retail position that has allowed me to put a large part of my earnings into a savings account. I hope to put away nearly £6000 come the start of my PhD, and my employer is allowing me to continue working during my PhD on a much reduced contract, so I'll be earning ~£300/month into the foreseeable. My place comes with tuition paid for, but no stipend for at least the first year. My supervisor has said that he may be able to get me funding for the second and third year hopefully. Obviously I want to try to keep my £6000 as savings, incase I have big expenditure like the one above, and live off my earnings and perhaps a small amount of my savings. I'm in the lucky position of being accepted to the university in my hometown, and my parents have said I can continue living there for the duration, if needs be, at minimal cost (~£150/month). How much have other put away as a rainy day fund? I've tried to account for every foreseeable expense (i.e. travel, equipment, clothing, rent, gym membership etc. etc.), but have you had any additional, unaccounted for expense? 

Sorry for the tome-like first post, but I'd really appreciate any advice. 

zt