Welcome Jade,
1. 8% + 18% employers' match? Grab this with both hands. Now is good.
I'll wait while you fill in the paperwork.
If it helps, don't think of tying this money up until you're 55; think of it as the chunk of your money that you get to spend after 55, but that contributes to your 'stache from now until then. Take it from a Zombie: check out
http://www.thefinancezombie.com/2015/11/the-bridge-to-financial-independence.html for more info about balancing the pre and post 55 spending.
2. Getting started with investing.
This will feel a bit scary at first, and that's okay, but you will learn as you go. Unless you have a particular reason for liking the FTSE100, I'd highly recommend Vanguard LifeStrategy 60 for someone in your situation. It is more diversified than the FTSE100, it has your 40% bonds built in and you can set it and forget it.
After you've learnt more you'll probably choose something slightly different, but VLS 60 is a great place to start. Trust me, I'm a random person on the internet.
Choose a low fee S&S ISA from this table
http://monevator.com/compare-uk-cheapest-online-brokers/. If you have been saving and thinking about FIRE for a while (which I 'm assuming as you have a paid off house), then think about how much you'll have in there in a couple of years, not just which one is best for your first £1,000. A fixed fee might be best.
If your cash savings represents a comfortable level of emergency funding (considering hourly/freelance wages), I'd leave that as it is (ie move the Santander money to other cash accounts - Moneysavingexpert has the list). So just put your extra £1,000 into an S&S ISA buying VLS 60. If you get more comfortable with investing then maybe divert some of the cash into the ISA as well (I tend to do this in March before the tax year ends).
As much as possible, ignore the value of your ISA. Set up a monthly direct debit and auto investment. Do not read the business news, do not check it more than once a quarter.
3. Saving rate
Is amazing, well done.
4. Other things
Your husband's pension isn't amazing, but is still 1% free money if you delay taking it for a decade (and I think this will increase over the next few years).
I'd hold off on a SIPP for now. The value is less clear cut the less tax you pay. If the access age is still 55 as you and your husband approach 55, consider putting the equivalent of all of your annual earnings in there for a couple of years to get a cheeky government top-up.
Check how much a new customer pays for the same AA cover, and then switch it between you and your husband as new customers instead of renewing (look at topcashback also).
Have you looked at whether the freelancer can claim back tax on professional fees and diesel?