Sudden jump in blood pressure

I normally have low to normal blood pressure - at the last m/w check (about 2 weeks ago) it was 65/110.
Well I felt quite light headed this morning and just generally unwell and thought if anything my bp had dropped as it has done that before but we measured it - my gran has a home measuring mch. Anyways my bp was 84/142 so really quite high for me. I'm having a little rest at the moment and begining to feel better. We'll measure it again in 20min or so and I'll call my m/w if it's still high but I just wonder has this happened to anyone before?
I'm trying not to worry too much at this stage but it just seems so strange...

142/84 is a little high. The bottom number (84) is actually really good so I wouldn't be concerned with that one. The only thing your MW may do is actually disregard those readings as they weren't done by her and she'll do a check for you and then make a decsion once she has seen you.

My bp at the start of pregnancy was 110-120/60-70 and now it's up at 130-140/80.

My bp and pulse both rocket after I've had a shower. So I learned from having a hospital stay

Having a wee rest should get it down again.
Maybe it's to do with the heat/stress over the last 2 weeks?

Yeah it's a funny thing. We took it 20min later and it was doen to 121/79. I rang my m/w too and she wasn't too concerned but said to get a rest, keep monitoring the baby movements and if it goes up again, to go and get checked at assesment unit. So far I've had a good rest and not feeling too bad.