Bigger D,
No, VFR 'CFI' in EASA system only needs PPL or CPL and certain hours (ie if PPL holder, and commercial theory passes if instructing regular PPL).
The 'CFII' ie EASA IRI, heli or aeroplane, needs plenty more IFR time - could be flight plan IFR time, not IMC, more if not VFR 'CFI' or 200 if EASA FI and doing short course to be instrument instructor.
Subject to having bit extra PIC/command hours (and not counting post-private dual/training) one can add heli or aeroplane FI to PPL, when talking about mainstream power flying. Other rules for TMG, sailplanes or not as common categories apply as well.
The CFR/FARs requirement to hold IR/IFR rating for instructors does NOT apply to gliding, helicopter etc. Only aeroplane, stateside. While it is beneficial to have more IR training, ordinary PPL training would not have more than couple hours basic IR training.
While it's been suggested to get some time skydiving, many UK clubs have higher hourly requirements for insurance, even if one can do it on PPL.
Glider towing - really depends on individual clubs although the minima and training is now stipulated in EASA Part.FCL. Most clubs want gliding experience (obvious reasons, ie not avoiding turbulence ~ LIFT, and knowing the edges of lift ie into sink, awareness of other gliders flying around, the procedures, appreciation of gentler tug flying when the the rear end of the rope etc). In the past, some clubs, namely around Bristol let experienced gliding guys tow with literally basic PPL, but most would want 100hrs TT as rough guide (trust me, there's still sharper upward learning curve flying in command after PPL flight test), other wanted Silver C being held for insurance reasons - or that as excuse but showing they put more weight on being glider pilot first.
You may get some cheaper hours flying with people not fussed about logging the time (agreed prior the flight), or friends as passengers etc, then while doing so, get involved in soaring - winch launch clubs are much cheaper to go solo and then just get aerotow checked out. Some flights in glider are now also part of the towing rating in EASA regs, too, anyway.
Some busier schools that do not have onsite or same airport maintenance for 50 or 100 hourly or annuals, may offer reduced 'reposition' rental rates. Win-win situation.
Even if you aren't in command, the flight experience may be handy, especially with someone instructor/CRI rated, so it's loggable. Exclusions apply, Eurocracy.. Not as simple as US system, so do check the legalities.
As mentioned, if you want to knock off some PIC time, consider joining flying group. Non-equity ones are safest bet against unexpected mx bills, certain deposit and monthly fees. It depends on your disposable income if it's worth being member year round, or just for the summer season. Cheaper than renting from schools in majority of low cost Cessnas/Pipers.
Few 'full EASA SEP aircraft' or whichever non-microlight name for CS-23 aircraft are also in shares, definitely recommend some tailwheel, which may be on permit to fly, reduced paperwork/costs even if heavy enough, but too old/vintage for EASA to bother with mx oversight, ie Cubs/Austers. Still kosher time towards FI rating.
Don't forget, if you save up, you can do some solo renting in countries with nice scenery and possibly lower hourly cost, depending on exchange rates, but if combining it with holiday, the extra travel/admin/insurance costs can be worth it.
Finally, once you do your hours to add FI to PPL(A) (150hrs command), you may consider doing FI course in Central Europe as it's roughly half price and could be done in a month or so, if planning it around your work in better weather month.
3500-5500 EUR sounds better than 6-9k GBP in UK, not considering housing/travel.
If doing the CPL theory, CATS are cheapest in the UK and most of Europe wouldn't have cheaper 'ATPL' theory courses. The IR side is pointless if you only ever gonna do PPL training. So just VFR CPL. The theory completion/passes certificate from any EASA country is good as the UK one and can save you 13x~69GBP vs 130-300EUR for whole lot and free resits. Can be done in a week if planned ahead and again, making the most of holidays at work, easyjet/RYR advance tickets to Budapest, Prague, Bratislava, somewhere in Poland. Czech Rep upped the ATPL/CPL fees to about 180eur/whole set, Hungary about the same currently, but weirder 'sitting' days, ie two days every week, two weeks are one sitting, so bit inconvenient for short trip. Slovakia's 10eur a subject at the moment, free resits. Poland would be about 200-300 eur mark for whole set as well. Elsewhere haven't needed researching myself. Never fancied UK CAA fees, the FRTOL I did was costly enough for bit of paper.
Well, gave you few ideas to cut the costs. Actually, you can even save on the silly UK CAA FI rating issue. If you manage moving your PPL to lower cost EASA country (meant to be half year living there etc, not too strictly enforced) but that also involves transfering medical records first - state of licence issue normally does keep the medical records, even if you do med exam in third party country, but then post the stuff to 'own CAA' wherever it is. Czech Rep for example, 20 or 50 eur adding FI rating to PPL. UK CAA tons wonga for flight test and then issue, combined. NO thanks.
There are some advantages to EASA, although it's bureaucratic hassle.